[maglev] Fix VisitLdaImmutableContextSlot

It should delegate to VisitLdaContextSlot.

Bug: v8:7700
Change-Id: I1591594648cfb038abccabb46a20c1b0c23b07a6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3602512
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80117}

src/maglev/maglev-graph-builder.cc

@@ -311,7 +311,7 @@ void MaglevGraphBuilder::VisitLdaContextSlot() {
 }
 void MaglevGraphBuilder::VisitLdaImmutableContextSlot() {
   // TODO(leszeks): Consider context specialising.
-  VisitLdaCurrentContextSlot();
+  VisitLdaContextSlot();
 }
 void MaglevGraphBuilder::VisitLdaCurrentContextSlot() {
   ValueNode* context = GetContext();