RETF exclusion regex should not be treated as case-insensitive

[Daimona]

The RETF exclusion regex uses the i modifier, but the AWB typo list is case-sensitive (and this is respected in the actual .replace() call), so it unnecessarily processes more rules than it should. Aside from performance, it results in a bunch of irrelevant rules being listed as "found" in the console message. This should be easily fixable by dropping the modifier and adjusting the File part of the regexp.