Remove BorrowKind glob, make names longer

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -816,7 +816,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     ) {
                         match captured_place.info.capture_kind {
                             ty::UpvarCapture::ByRef(
-                                ty::BorrowKind::MutBorrow | ty::BorrowKind::UniqueImmBorrow,
+                                ty::BorrowKind::Mutable | ty::BorrowKind::UniqueImmutable,
                             ) => {
                                 capture_reason = format!("mutable borrow of `{upvar}`");
                             }