Update installation.md (#12621)

Update openapi-generator-cli.jar to the latest 6.0.0 version

docs/installation.md

@@ -103,18 +103,18 @@ docker run --rm \
 <!-- RELEASE_VERSION -->
 If you're looking for the latest stable version, you can grab it directly from Maven.org (Java 8 runtime at a minimum):
 
-JAR location: `https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/5.3.0/openapi-generator-cli-5.3.0.jar`
+JAR location: `https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/6.0.0/openapi-generator-cli-6.0.0.jar`
 
 For **Mac/Linux** users:
 
 ```bash
-wget https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/5.3.0/openapi-generator-cli-5.3.0.jar -O openapi-generator-cli.jar
+wget https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/6.0.0/openapi-generator-cli-6.0.0.jar -O openapi-generator-cli.jar
 ```
 
 For **Windows** users, you will need to install [wget](http://gnuwin32.sourceforge.net/packages/wget.htm) or you can use Invoke-WebRequest in PowerShell (3.0+), e.g.
 
 ```powershell
-Invoke-WebRequest -OutFile openapi-generator-cli.jar https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/5.3.0/openapi-generator-cli-5.3.0.jar
+Invoke-WebRequest -OutFile openapi-generator-cli.jar https://repo1.maven.org/maven2/org/openapitools/openapi-generator-cli/6.0.0/openapi-generator-cli-6.0.0.jar
 ```
 <!-- /RELEASE_VERSION -->