Remove scrutinee_hir_id from ExprKind::Match

It is unused

Author: bjorn3

Diff for: compiler/rustc_middle/src/thir.rs

@@ -376,7 +376,6 @@ pub enum ExprKind<'tcx> {
     /// A `match` expression.
     Match {
         scrutinee: ExprId,
-        scrutinee_hir_id: HirId,
         arms: Box<[ArmId]>,
         match_source: MatchSource,
     },

Diff for: compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -828,7 +828,6 @@ impl<'tcx> ThirBuildCx<'tcx> {
             },
             hir::ExprKind::Match(discr, arms, match_source) => ExprKind::Match {
                 scrutinee: self.mirror_expr(discr),
-                scrutinee_hir_id: discr.hir_id,
                 arms: arms.iter().map(|a| self.convert_arm(a)).collect(),
                 match_source,
             },

Diff for: compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -151,7 +151,7 @@ impl<'p, 'tcx> Visitor<'p, 'tcx> for MatchVisitor<'p, 'tcx> {
                 }
                 return;
             }
-            ExprKind::Match { scrutinee, scrutinee_hir_id: _, box ref arms, match_source } => {
+            ExprKind::Match { scrutinee, box ref arms, match_source } => {
                 self.check_match(scrutinee, arms, match_source, ex.span);
             }
             ExprKind::Let { box ref pat, expr } => {