Fix AGENTS.md: use 'mvn verify -pl :org.eclipse.swt.tests' for running

specific tests

Prevent the procedure from failing on MacOS and Linux which have no
platform specific tests, requiring
`surefire.failIfNoSpecifiedTests=false`.

Author: basilevs

AGENTS.md

@@ -99,8 +99,8 @@ If needed, add packages to `Import-Package` or `Require-Bundle`.
 # Run all tests
 mvn clean verify
 
-# Run specific test class
-mvn test -Dtest=ClassName
+# Run specific test class (append `#testMethodName` for a single test)
+mvn verify -pl :THE_BUNDLE_WITH_THE_ACTUAL_TEST -am -DskipNativeTests=false -Dsurefire.failIfNoSpecifiedTests=false -Dtest=ClassName
 ```
 
 ### Test Location