[python/pyre.vim] use pyrefly executable (#4972)

https://github.com/facebook/pyrefly

The pyre project has evolved to pyrefly. This replaces the pyre linter
with a pyrefly one and removes the test files that were added for
finding the project root in the old pyre world.

Co-authored-by: Oliver Ruben Albertini <oliverruben@gmail.com>

test/completion/test_ale_import_command.vader

@@ -14,7 +14,7 @@ Before:
   let g:ale_completion_enabled = 0
   let g:ale_completion_autoimport = 0
   let g:ale_completion_max_suggestions = 50
-  let g:ale_linters = {'typescript': ['tsserver'], 'python': ['pyre']}
+  let g:ale_linters = {'typescript': ['tsserver'], 'python': ['pyrefly']}
   unlet! b:ale_linters
 
   let g:server_started_value = 1