Update astyle to 3.4.12

as astyle 3.1 is no longer available in the latest FreeBSD.

Also, astyle upstream repository has been moved to GitLab. Switched git
to obtain astyle source.

https://gitlab.com/saalen/astyle

.github/workflows/build.yml

@@ -194,8 +194,8 @@ jobs:
       CC: gcc
       # This is required to use a version of astyle other than that
       # supplied with the operating system
-      ASTYLE_VER: 3.1
-      ASTYLE_REPO: https://svn.code.sf.net/p/astyle/code/tags
+      ASTYLE_VER: 3.4.12
+      ASTYLE_REPO: https://gitlab.com/saalen/astyle.git
     steps:
       # Set steps.os.outputs.image to the specific OS (e.g. 'ubuntu20')
       - name: Get operating system name and version.