request: remove SC2089 and SC2090

The SC2089 and SC2090 are rather strange. 2090 lacks a complete description. The wiki page is bare, linking to 2089: https://www.shellcheck.net/wiki/SC2090 The rules arbitrarily ban quotes and backslashes in strings, just because sometimes shells handle these implicitly. There's no automatable way for a linter to know the user's intent. Very many things require quotes and backslashes. These rules are the equivalent of slapping a grocer in the face every time they restock oranges, simply because oranges sometimes contain seeds. The number of valid use cases eclipse the number of hazards.