fixes #14869

changelog: stop triggering similar_names for 3-character names

Added a simple check if both chars are of length 3
If they are, we skip the check for that pair.

This won't handle the 4 v 3 case.
Not sure if this was the intent of the issue.

Also saw we have some hardcoded exemptions for set, get and lhs, rhs
Tried removing them thinking they would be handled by the new condition.
But we have to keep because they allow for bla_lhs v bla_rhs to be skipped

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