Auto merge of #68080 - varkor:declared-here, r=petrochenkov

Auto merge of #68080 - varkor:declared-here, r=petrochenkov

Address inconsistency in using "is" with "declared here"

"is" was generally used for NLL diagnostics, but not other diagnostics. Using "is" makes the diagnostics sound more natural and readable, so it seems sensible to commit to them throughout.

r? @Centril