[heap] Remove custom visitor for JSRegex.

JSRegex does not have custom body descriptor and uses JSObject body
descriptor, so it should just use JSObject visitor id.

Bug: chromium:825828
Change-Id: Iae22315da7ab83bb4ac919586c883120621761c8
Reviewed-on: https://chromium-review.googlesource.com/980752Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52228}

src/heap/objects-visiting.h

@@ -40,7 +40,6 @@ class JSWeakCollection;
   V(JSArrayBuffer)               \
   V(JSFunction)                  \
   V(JSObject)                    \
-  V(JSRegExp)                    \
   V(JSWeakCollection)            \
   V(Map)                         \
   V(Oddball)                     \

src/objects.cc

@@ -3037,8 +3037,6 @@ VisitorId Map::GetVisitorId(Map* map) {
     case JS_WEAK_SET_TYPE:
       return kVisitJSWeakCollection;
 
-    case JS_REGEXP_TYPE:
-      return kVisitJSRegExp;
 
     case SHARED_FUNCTION_INFO_TYPE:
       return kVisitSharedFunctionInfo;
@@ -3090,6 +3088,7 @@ VisitorId Map::GetVisitorId(Map* map) {
     case JS_MAP_VALUE_ITERATOR_TYPE:
     case JS_STRING_ITERATOR_TYPE:
     case JS_PROMISE_TYPE:
+    case JS_REGEXP_TYPE:
     case WASM_MEMORY_TYPE:
     case WASM_MODULE_TYPE:
     case WASM_TABLE_TYPE:

src/objects/map.h

@@ -38,7 +38,6 @@ namespace internal {
   V(JSFunction)            \
   V(JSObject)              \
   V(JSObjectFast)          \
-  V(JSRegExp)              \
   V(JSWeakCollection)      \
   V(Map)                   \
   V(NativeContext)         \