chore(lint): Remove unused null coalescing operator

[effigies]

Was alerted while building a project using cliffy:

    https://deno.land/x/cliffy@v1.0.0-rc.3/command/help/_help_generator.ts:354:59:
      354 │   return string?.charAt(0).toUpperCase() + string.slice(1) ?? "";
          ╵                                                            ~~

  The left operand of the "??" operator here will never be null or undefined, so it will always be
  returned. This usually indicates a bug in your code:

    https://deno.land/x/cliffy@v1.0.0-rc.3/command/help/_help_generator.ts:354:9:
      354 │   return string?.charAt(0).toUpperCase() + string.slice(1) ?? "";
          ╵          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

for the input "", the return value is already "". null and undefined both raise TypeErrors.

[effigies]

It looks like, in d3c2fa1, you went from

function capitalize( string: string ): string {
    if ( !string ) {
        return '';
    }
    return string.charAt( 0 ).toUpperCase() + string.slice( 1 );
}

to

function capitalize( string: string ): string {
    return string?.charAt( 0 ).toUpperCase() + string.slice( 1 ) ?? '';
}

I suppose you were previously getting capitalize(null) == "" and capitalize(undefined) == "" before, but apparently the TypeError that now results hasn't been a problem in the last 4 years.

[c4spar]

Thx @effigies! LGTM!