[SPARK-40665][CONNECT][FOLLOW-UP] Fix connector/connect/dev/generate_protos.sh

[zhengruifeng]

What changes were proposed in this pull request?

Fix the path in connector/connect/dev/generate_protos.sh

Why are the changes needed?

(spark_dev) ➜  dev git:(master) pwd
/Users/ruifeng.zheng/Dev/spark/connector/connect/dev
(spark_dev) ➜  dev git:(master) ./generate_protos.sh
+++ dirname ./generate_protos.sh
++ cd ./../..
++ pwd
+ SPARK_HOME=/Users/ruifeng.zheng/Dev/spark/connector
+ cd /Users/ruifeng.zheng/Dev/spark/connector
+ pushd connector/connect/src/main
./generate_protos.sh: line 22: pushd: connector/connect/src/main: No such file or directory

Does this PR introduce any user-facing change?

No

How was this patch tested?

manually check

[zhengruifeng]

cc @HyukjinKwon

[HyukjinKwon]

Merged to master.