Corrected header line of analyze_driver_vs_reference

The header line said “driver vs reference” whereas the error line said
“reference -> driver”. Updated the header line to be consistent with the
error line.

Signed-off-by: Sam Berry <sam.berry@arm.com>
diff --git a/tests/scripts/analyze_outcomes.py b/tests/scripts/analyze_outcomes.py
index eb24694..fcf6d32 100755
--- a/tests/scripts/analyze_outcomes.py
+++ b/tests/scripts/analyze_outcomes.py
@@ -129,8 +129,8 @@
 def analyze_driver_vs_reference(results: Results, outcomes: Outcomes,
                                 component_ref: str, component_driver: str,
                                 ignored_suites: typing.List[str], ignored_tests=None) -> None:
-    """Check that all tests passing in the reference component are also
-    passing in the corresponding driver component.
+    """Check that all tests passing in the driver component are also
+    passing in the corresponding reference component.
     Skip:
     - full test suites provided in ignored_suites list
     - only some specific test inside a test suite, for which the corresponding