Fix error count calculation in compliance check

I just noticed this line which can either be deleted or added via += not sure which one is correct

Signed-off-by: gerbsen <1186245+gerbsen@users.noreply.github.com>

Author: gerbsen

Tests/scs-compliance-check.py

@@ -231,7 +231,7 @@ def run(self, check, testcases=()):
         self.num_abort += invocation["critical"]
         self.num_error += invocation["error"]
         # count failed testcases because they need not be reported redundantly on the error channel
-        self.num_error + len([value for value in invocation['results'].values() if value < 0])
+        self.num_error += len([value for value in invocation['results'].values() if value < 0])
         return invocation