[rbi] Remove highlights from errors.

[gottesmm]

I have noticed over time when working on the command line, we often times highlight too large of an expression due to the locations provided to us by earlier parts of the compiler. This isn't technically necessary and the following doesn't look nice... so remove it.

test5.swift:171:16: error: sending 'x' risks causing data races [#SendingRisksDataRace]
169 |   let _ = {
170 |     nonescapingAsyncUse { @MainActor in
171 | _� _� _� _� _�u_�s_�e_�V_�a_�l_�u_�e_�(_�x_�)
    |                |- error: sending 'x' risks causing data races [#SendingRisksDataRace]
    |                `- note: task-isolated 'x' is captured by a main actor-isolated closure. main actor-isolated uses in closure may race against later nonisolated uses
172 |     }
173 |   }

[gottesmm]

@swift-ci smoke test