[Bug] CI not failing on failures running unit test job

[cretz]

Describe the bug

Before #765, unit test actions like https://github.com/temporalio/samples-java/actions/runs/20075490738/job/57588618666 were failing with:

unit-test-1  | > Task :core:compileJava FAILED
unit-test-1  | /temporal-java-samples/core/src/main/java/io/temporal/samples/envconfig/LoadFromFile.java:3: warning: [NotJavadoc] Avoid using `/**` for comments which aren't actually Javadoc.
unit-test-1  | /**
unit-test-1  | ^
unit-test-1  |     (see https://errorprone.info/bugpattern/NotJavadoc)
unit-test-1  |   Did you mean '/*'?
unit-test-1  | /temporal-java-samples/core/src/main/java/io/temporal/samples/envconfig/LoadFromFile.java:83: warning: [NotJavadoc] Avoid using `/**` for comments which aren't actually Javadoc.
unit-test-1  | /**
unit-test-1  | ^
unit-test-1  |     (see https://errorprone.info/bugpattern/NotJavadoc)
unit-test-1  |   Did you mean '/*'?
unit-test-1  | error: warnings found and -Werror specified
unit-test-1  | Note: Some input files use or override a deprecated API.
unit-test-1  | Note: Recompile with -Xlint:deprecation for details.
unit-test-1  | Note: Some input files use unchecked or unsafe operations.
unit-test-1  | Note: Recompile with -Xlint:unchecked for details.
unit-test-1  | 1 error
unit-test-1  | 2 warnings
unit-test-1  | 
unit-test-1  | FAILURE: Build failed with an exception.
unit-test-1  | 
unit-test-1  | * What went wrong:
unit-test-1  | Execution failed for task ':core:compileJava'.
unit-test-1  | > Compilation failed; see the compiler error output for details.
unit-test-1  | 
unit-test-1  | * Try:
unit-test-1  | > Run with --info option to get more log output.
unit-test-1  | > Run with --scan to get full insights.
unit-test-1  | 
unit-test-1  | BUILD FAILED in 45s
unit-test-1  | 
unit-test-1  | Deprecated Gradle features were used in this build, making it incompatible with Gradle 9.0.
unit-test-1  | 
unit-test-1  | You can use '--warning-mode all' to show the individual deprecation warnings and determine if they come from your own scripts or plugins.
unit-test-1  | 
unit-test-1  | For more on this, please refer to https://docs.gradle.org/8.10.2/userguide/command_line_interface.html#sec:command_line_warnings in the Gradle documentation.
unit-test-1  | 4 actionable tasks: 4 executed

unit-test-1 exited with code 1

But the unit test job was still passing. Make sure the unit test job fails if the unit test piece fails.