chore: update support version and change default version to 18

Ref to f91c446, also bump default version.

Author: shenxianpeng

action.yml

@@ -39,12 +39,12 @@ inputs:
   version:
     description: |
       The desired version of the [clang-tools](https://github.com/cpp-linter/clang-tools-pip) to use.
-      Accepted options are strings which can be 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, or 8.
+      Accepted options are strings which can be 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10 or 9.
 
       - Set this option to a blank string (`''`) to use the platform's default installed version.
       - This value can also be a path to where the clang tools are installed (if using a custom install location).
     required: false
-    default: 16
+    default: 18
   verbosity:
     description: |
       This controls the action's verbosity in the workflow's logs.