fix(abnf-checker): return error on example error

We just printed the error before but not set exit code.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

docs/specs/om/open_metrics_spec_2_0.md

@@ -1184,3 +1184,4 @@ OpenMetrics would like to register two MIME types, `application/openmetrics-text
 <!---
 # EDITOR’S NOTE: We would like to thank Sumeer Bhola, but kramdown 2.x does not support `Contributor:` any more so we will add this by hand once consensus has been achieved.
 -->
+

openmetrics-spec-tests/check_openmetrics_spec.py

@@ -105,9 +105,12 @@ if __name__ == "__main__":
         print(f"Error parsing ABNF: {e}")
         sys.exit(1)
     print("ABNF parsed successfully.")
+    exit_code = 0
     for ex in examples(filename):
         try:
             Grammar.get(start_node).parse_all(ex.content)
             print(f"Example parsed successfully: {ex.line_number}: {ex.content[:30]}...")  # Print first 30 chars
         except Exception as e:
             print(f"Error parsing example at line {ex.line_number}: {e}\nExample: {ex.content[:30]}...")
+            exit_code = 2
+    sys.exit(exit_code)