chore: remove centralizable repo config

- Remove .github conf folder from Flarum packages

- Remove styleci config from all packages

php-packages/testing/.styleci.yml

@@ -1,18 +0,0 @@
-preset: recommended
-
-enabled:
-  - logical_not_operators_with_successor_space
-
-disabled:
-  - align_double_arrow
-  - blank_line_after_opening_tag
-  - multiline_array_trailing_comma
-  - new_with_braces
-  - phpdoc_align
-  - phpdoc_order
-  - phpdoc_separation
-  - phpdoc_types
-
-finder:
-  exclude:
-    - "stubs"