Update Python vimrc detection to 3.10

CI build has been updated to build MacVim against Python 3.10, so we
want to update the other detection to use 3.10 as well. Also added a
comment to CI file to make sure we remember to update the vimrc file
when updating the version.

Author: ychin

.github/workflows/ci-macvim.yaml

@@ -17,7 +17,7 @@ env:
   vi_cv_path_ruby: /usr/local/opt/ruby/bin/ruby
   vi_cv_dll_name_perl: /System/Library/Perl/5.18/darwin-thread-multi-2level/CORE/libperl.dylib
   vi_cv_dll_name_python: /System/Library/Frameworks/Python.framework/Versions/2.7/Python
-  vi_cv_dll_name_python3: /usr/local/Frameworks/Python.framework/Versions/3.10/Python
+  vi_cv_dll_name_python3: /usr/local/Frameworks/Python.framework/Versions/3.10/Python # Make sure to keep src/MacVim/vimrc synced with the Python version here for the Python DLL detection logic.
   vi_cv_dll_name_python3_arm64: /opt/homebrew/Frameworks/Python.framework/Versions/3.10/Python
   vi_cv_dll_name_ruby: /usr/local/opt/ruby/lib/libruby.dylib
   vi_cv_dll_name_ruby_arm64: /opt/homebrew/opt/ruby/lib/libruby.dylib

src/MacVim/vimrc

@@ -32,12 +32,13 @@ endif
 " or an installation from python.org:
 if exists("&pythonthreedll") && exists("&pythonthreehome") &&
       \ !filereadable(&pythonthreedll)
-  if filereadable("/opt/local/Library/Frameworks/Python.framework/Versions/3.9/Python")
-    " MacPorts python 3.9
-    set pythonthreedll=/opt/local/Library/Frameworks/Python.framework/Versions/3.9/Python
-  elseif filereadable("/Library/Frameworks/Python.framework/Versions/3.9/Python")
+  if filereadable("/opt/local/Library/Frameworks/Python.framework/Versions/3.10/Python")
+    " MacPorts python 3.10
+    set pythonthreedll=/opt/local/Library/Frameworks/Python.framework/Versions/3.10/Python
+  elseif filereadable("/Library/Frameworks/Python.framework/Versions/3.10/Python")
     " https://www.python.org/downloads/mac-osx/
-    set pythonthreedll=/Library/Frameworks/Python.framework/Versions/3.9/Python
+    set pythonthreedll=/Library/Frameworks/Python.framework/Versions/3.10/Python
   endif
 endif
 
+" vim: sw=2 ts=2 et