Fix Pylint-detected function argument syntax error

Signed-off-by: Yuto Takano <yuto.takano@arm.com>
diff --git a/tests/scripts/check-names.py b/tests/scripts/check-names.py
index 3310ae2..349e66b 100755
--- a/tests/scripts/check-names.py
+++ b/tests/scripts/check-names.py
@@ -560,7 +560,7 @@
 
         return symbols
 
-    def perform_checks(self, show_problems: True):
+    def perform_checks(self, show_problems=True):
         """
         Perform each check in order, output its PASS/FAIL status. Maintain an
         overall test status, and output that at the end.