InlineExpectationsTest: Add quote around missing tag

To aid with quickly scanning where the missing tag is. I just had to do
this myself looking over some test failures, and it all just blurred
into each other in the logs.

see https://github.com/github/codeql/actions/runs/3332266045/jobs/5512944867#step:5:467

Author: RasmusWL

python/ql/test/TestUtilities/InlineExpectationsTest.qll

@@ -156,8 +156,8 @@ abstract class InlineExpectationsTest extends string {
       not actualResult.getTag() = this.getARelevantTag() and
       element = actualResult and
       message =
-        "Tag mismatch: Actual result with tag " + actualResult.getTag() +
-          " that is not part of getARelevantTag()"
+        "Tag mismatch: Actual result with tag '" + actualResult.getTag() +
+          "' that is not part of getARelevantTag()"
     )
     or
     exists(ValidExpectation expectation |

python/ql/test/library-tests/InlineExpectationsTest/missing-relevant-tag/Test.expected

@@ -1,2 +1,2 @@
-| test.py:1:1:1:3 | foo | Tag mismatch: Actual result with tag foo that is not part of getARelevantTag() |
-| test.py:4:1:4:3 | foo | Tag mismatch: Actual result with tag foo that is not part of getARelevantTag() |
+| test.py:1:1:1:3 | foo | Tag mismatch: Actual result with tag 'foo' that is not part of getARelevantTag() |
+| test.py:4:1:4:3 | foo | Tag mismatch: Actual result with tag 'foo' that is not part of getARelevantTag() |