[cleanup] Fix typo

Bug: v8:7310
Change-Id: I2e3c324babc4e7e51791c44290dffcf8829c15ce
Reviewed-on: https://chromium-review.googlesource.com/946252Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51701}

src/compiler/js-call-reducer.cc

@@ -3826,7 +3826,7 @@ Reduction JSCallReducer::ReduceStringPrototypeSlice(Node* node) {
   return Replace(result_string);
 }
 
-// ES #sec-string.prototype.slice
+// ES #sec-string.prototype.substr
 Reduction JSCallReducer::ReduceStringPrototypeSubstr(Node* node) {
   if (node->op()->ValueInputCount() < 3) return NoChange();
   CallParameters const& p = CallParametersOf(node->op());