Add neovim 0.6 to run-tests (#3998)

* Update test scripts
* Remove neovim 0.3 and 0.4
* Add neovim 0.6.1

Co-authored-by: Horacio Sanson <horacio@allm.inc>
Co-authored-by: w0rp <devw0rp@gmail.com>

test/linter/test_php_langserver.vader

@@ -5,6 +5,8 @@ After:
   call ale#assert#TearDownLinterTest()
 
 Execute(The default executable path should be correct):
+  call ale#test#SetFilename('../test-files/dummy')
+
   AssertLinter 'php-language-server.php',
   \ 'php ' . ale#Escape('php-language-server.php')