fix broken installation page link

Summary:
An user in github reported an issue that the installation link is broken. Somehow,
docs/installation/installation.md cannot be referenced by `/docs/installation/installation`, but
only by `/docs/installation`. The root cause could not figured out yet, but this change fixes it as
such for now.

Reviewed By: jiayuebao

Differential Revision: D43757739

fbshipit-source-id: 4abd3208800c0b68e9162d381f6395897f047b24

Author: Jaesoo Lee

README.md

@@ -50,7 +50,7 @@ cd CacheLib
 Re-running `./contrib/build.sh` will update CacheLib and its dependencies
 to their latest versions and rebuild them.
 
-See [build](https://cachelib.org/docs/installation/installation) for more details about
+See [build](https://cachelib.org/docs/installation/) for more details about
 the building and installation process.
 
 

website/docs/Cache_Library_User_Guides/Cachebench_FB_HW_eval.md

@@ -19,7 +19,7 @@ sufficient free memory (50+GB) and SSD capacity (1TB).
 
 ## Set up the SSD devices
 
-To gather SSD performance metrics, the SSD must be setup first. Cachebench (and CacheLib) supports using various types of devices for NVM cache including a raw block device or a regular file. When one wants to use multiple SSDs as NVM cache, the CacheLib also provides a native support for RAID0 (i.e., striping). 
+To gather SSD performance metrics, the SSD must be setup first. Cachebench (and CacheLib) supports using various types of devices for NVM cache including a raw block device or a regular file. When one wants to use multiple SSDs as NVM cache, the CacheLib also provides a native support for RAID0 (i.e., striping).
 
 Optionally, as an example, an user can setup and use md devices as follows. In this example, the md device is created from two ssd devices to be used as a raw block device in CacheBench.
 
@@ -143,7 +143,7 @@ mdadm --create /dev/md0 --force --raid-devices=2 --level=0 --chunk=256 /dev/nvme
     make install
     ```
 
-See [build and installation](/docs/installation/installation) for further details.
+See [build and installation](/docs/installation) for further details.
 
 ## Running the benchmark for SSD perf testing
 
@@ -197,7 +197,6 @@ For a full list of options that can be configured, see [configuring cachebench](
    using the `--progress` and specifying a duration in seconds.
    If `--progress-stats-file` is also specified, on every progress
    interval, `cachebench` would log the internal stats to the specified file.
-   
 ## Running cachebench with the trace workload
 
 Meta is sharing anonymized traces captured from large scale production cache services. These traces are licensed under the same license as CacheLib. They are meant to help academic and industry researchers to optimize for our caching workloads. One can freely download it from our AWS S3 bucket and run the CacheBench to replay the trace with varying configuration as follows.

website/docs/Cache_Library_User_Guides/Cachebench_Overview.md

@@ -53,6 +53,6 @@ developer's need. The following are few examples.
 
 ## Building  cachebench
 
-Follow instructions in [Installation](/docs/installation/installation) to build
+Follow instructions in [Installation](/docs/installation) to build
 cachebench. This should install cachebench in your local machine under
 ```opt/cachelib/bin/cachebench```

website/docs/installation/testing.md

@@ -11,7 +11,7 @@ of the cache infrastructure.
 ## Building CacheLib Unit Tests
 
 To build the cachelib unit tests, use one of the following commands
-(see [installation](docs/installation/installation) instructions for more details):
+(see [installation](/docs/installation) instructions for more details):
 
 1. Use `./contrib/build.sh` script with the `-T` option.
 2. Use `./contrib/build-package.sh -t cachelib` (with the `-t` option)
@@ -42,7 +42,7 @@ Running a single unit test binary:
 
 ```sh
 $ cd opt/cachelib/tests
-$ ./allocator-test-ItemTest 
+$ ./allocator-test-ItemTest
 [==========] Running 6 tests from 1 test suite.
 [----------] Global test environment set-up.
 [----------] 6 tests from ItemTest