Remove `assets` and `templates` from `.php_cs` excluded files

[mallorydxw]

wordpress-template/wp-content/themes/theme/.php_cs

Line 5 in 4a42793

->exclude('assets')

assets shouldn't include PHP code anyway - and won't be a gigantic mess like node_modules or entirely Gruntfile-generated like static

wordpress-template/wp-content/themes/theme/.php_cs

Line 7 in 4a42793

->exclude('templates')

templates contains PHP that doesn't conform to our usual standards (i.e., not classes) so it should be exempt from some checks. But probably not from style checks.