only test 5.4 for performance reasons

Author: Daniel Marjamäki

.github/workflows/gcc-versions.yml

@@ -21,7 +21,8 @@ jobs:
 
     strategy:
       matrix:
-        image: ["ghcr.io/cppcheck-opensource/gcc:5.4", "ghcr.io/cppcheck-opensource/gcc:6.5", "ghcr.io/cppcheck-opensource/gcc:7.5", "ghcr.io/cppcheck-opensource/gcc:8.5", "ghcr.io/cppcheck-opensource/gcc:9.5"]
+        #image: ["ghcr.io/cppcheck-opensource/gcc:5.4", "ghcr.io/cppcheck-opensource/gcc:6.5", "ghcr.io/cppcheck-opensource/gcc:7.5", "ghcr.io/cppcheck-opensource/gcc:8.5", "ghcr.io/cppcheck-opensource/gcc:9.5"]
+        image: ["ghcr.io/cppcheck-opensource/gcc:5.4"]
       fail-fast: false
 
     runs-on: ubuntu-22.04