Prepare 3.2.3 release

[wing328]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
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Description of the PR

To prepare the 3.2.3 release

[jmini]

About a6191ea: If you would regenerate the samples/meta-codegen content with bin/meta-codegen.sh, then you would have the same result.

But we are not generating our samples when we perform the release, so the solution of using bin/utils/release_version_update.sh the version is OK for me.

[jmini]

Release published:
https://github.com/OpenAPITools/openapi-generator/releases/tag/v3.2.3

[jmini]

Result of command ruby bin/utils/release_checkout.rb 3.2.3:

Running checkout on OpenAPI Generator release 3.2.3
Checking homebrew forumla ... [ERROR]
> https://raw.githubusercontent.com/Homebrew/homebrew-core/master/Formula/openapi-generator.rb not yet updated with https://search.maven.org/remotecontent?filepath=org/openapitools/openapi-generator-cli/3.2.3/openapi-generator-cli-3.2.3.jar
Checking openapi-generator JAR ... [OK]
Checking openapi-generator-cli JAR ... [OK]
Checking openapi-generator-maven-plugin JAR ... [OK]
Checking openapi-generator-gradle-plugin JAR ... [ERROR]
> http://central.maven.org/maven2/org/openapitools/openapi-generator-gradle-plugin/3.2.3/openapi-generator-gradle-plugin-3.2.3.jar not found
Checking openapi-generator-online JAR ... [OK]
Checking openapi-generator-project pom.xml ... [OK]
Checking openapi-generator README.md ... [OK]
Checking openapi-generator-online docker ... [OK]
Checking openapi-generator-cli docker ... [OK]

[jmini]

PR #938 is merged to master. Ready to work on 3.3.0-SNAPSHOT.

[jmini]

Homebrew formula Homebrew/homebrew-core#31602

[jmini]

gradle plugin 3.2.3 is publised on sonatype releases.

https://oss.sonatype.org/content/repositories/releases/

It will appear on maven-central soon.