Fix negative test filter on Windows

At least we can now see the failure from the previous run:

- https://buildkite.com/bazel/rules-scala-scala/builds/5513#0195e78b-6abc-42ea-95ee-8ddce41a64fb

```txt
FAIL: //src/java/io/bazel/rulesscala/worker:worker_test
  (see C:/tools/msys64/home/b/_bazel_b/2cvmpa54/execroot/_main/bazel-out/x64_windows-fastbuild/testlogs/src/java/io/bazel/rulesscala/worker/worker_test/test.log)
INFO: From Testing //src/java/io/bazel/rulesscala/worker:worker_test:
==================== Test output for //src/java/io/bazel/rulesscala/worker:worker_test:
JUnit4 Test Runner
...E
Time: 0.432
There was 1 failure:
1) testPersistentWorkerArgsfile(io.bazel.rulesscala.worker.WorkerTest)
org.junit.ComparisonFailure: expected:<line 1[
--flag_1
]ome arg
> but was:<line 1[
--flag_1
some arg]
>
	at org.junit.Assert.assertEquals(Assert.java:117)
	at org.junit.Assert.assertEquals(Assert.java:146)
	at io.bazel.rulesscala.worker.WorkerTest.testPersistentWorkerArgsfile(WorkerTest.java:73)
FAILURES!!!
Tests run: 3,  Failures: 1
BazelTestRunner exiting with a return value of 1
JVM shutdown hooks (if any) will run now.
The JVM will exit once they complete.
-- JVM shutdown starting at 2025-03-30 14:55:38 --
```

Author: mbland

test_rules_scala.sh

@@ -16,7 +16,7 @@ test_output_flag="--test_output=errors"
 test_target_filter=""
 
 if is_windows; then
-  test_target_filter="-- //src/java/io/bazel/rulesscala/worker:worker_test"
+  test_target_filter="-- -//src/java/io/bazel/rulesscala/worker:worker_test"
 fi
 
 "${test_dir}"/test_bzlmod_macros.sh