Rule Merger: no-unnecessary-type-assertion is not needed

[KingDarBoja]

🚀 Feature Request

Existing Behavior

We do have declared a merger for the @typescript-eslint/no-unnecessary-type-assertion rule but this doesn't seems to require it as it is pretty much a 1:1 converter with the whitelist of types to ignore being mapped into typesToIgnore as stated in the ESLint docs.

• TSLint Rule: no-unnecessary-type-assertion
• ESLint Rule: @typescript-eslint/no-unnecessary-type-assertion

Change Proposal

Cleanup the rule by removing the merger and adding the logic into the converter.

[JoshuaKGoldberg]

...huh! I wonder if it used to be necessary, but isn't anymore?