Re-add Guava to Bazel TestRunner

It was removed in d6ad383. Accidentally, this is a breaking change, because Guava is incorrectly added from TestRunner to Java library.

Breaking change is preventing java_tools to be released and cherry-picked onto Bazel 6.2.0

I tested this manually on one of the downstream breakages.

PiperOrigin-RevId: 525697087
Change-Id: Ic4ade4398ea422d982fe0fe96d2854ef5aeae568

src/java_tools/junitrunner/java/com/google/testing/junit/runner/BUILD

@@ -13,6 +13,10 @@ java_library(
         "BazelTestRunner.java",
     ],
     deps = [
+        # Testrunner shouldn't be added to compile-time deps of java_library.
+        # Because of this removing Guava dependecy is a breaking change.
+        # TODO(b/113524892): Short time before Bazel LTS 7 is cut, remove Guava and release java_tools
+        "//third_party:guava",  # build_cleaner: keep
         "//src/java_tools/junitrunner/java/com/google/testing/junit/runner/internal",
         "//src/java_tools/junitrunner/java/com/google/testing/junit/runner/junit4",
     ],