Revert of Ship --harmony-regexp-exec (patchset #3 id:40001 of...

Revert of Ship --harmony-regexp-exec (patchset #3 id:40001 of https://codereview.chromium.org/1847103002/ )

Reason for revert:
breaks some chromium browser_tests: https://codereview.chromium.org/1848233002/

Original issue's description:
> Ship --harmony-regexp-exec
>
> There are still spec compliance fixes to be made, but this patch
> turns the flag to shipping to make sure we get more canary coverage
> and performance data from the bots.
>
> BUG=v8:4602
> LOG=y
>
> Committed: https://crrev.com/84492bb66b340f4e0df36758e98fddbb10b5d1dc
> Cr-Commit-Position: refs/heads/master@{#35181}

TBR=littledan@chromium.org,adamk@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:4602

Review URL: https://codereview.chromium.org/1852673003

Cr-Commit-Position: refs/heads/master@{#35198}

src/flag-definitions.h

@@ -204,6 +204,7 @@ DEFINE_IMPLICATION(es_staging, move_object_start)
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                                    \
+  V(harmony_regexp_exec, "harmony RegExp exec override behavior")            \
   V(harmony_regexp_lookbehind, "harmony regexp lookbehind")                  \
   V(harmony_tailcalls, "harmony tail calls")                                 \
   V(harmony_object_values_entries, "harmony Object.values / Object.entries") \
@@ -218,7 +219,6 @@ DEFINE_IMPLICATION(es_staging, move_object_start)
   V(harmony_instanceof, "harmony instanceof support")                 \
   V(harmony_iterator_close, "harmony iterator finalization")          \
   V(harmony_unicode_regexps, "harmony unicode regexps")               \
-  V(harmony_regexp_exec, "harmony RegExp exec override behavior")     \
   V(harmony_sloppy, "harmony features in sloppy mode")                \
   V(harmony_sloppy_let, "harmony let in sloppy mode")                 \
   V(harmony_sloppy_function, "harmony sloppy function block scoping") \

test/mjsunit/es6/regexp-flags.js

@@ -44,11 +44,9 @@ assertEquals(2, get_count);
 // Overridden flag getters affects the flags getter.
 assertEquals("gi", r3.flags);
 assertEquals(4, get_count);
-// Overridden flag getters affect string.replace
-// TODO(adamk): Add more tests here once we've switched
-// to use [[OriginalFlags]] in more cases.
+// Overridden flag getters do not affect the internal flags.
 assertEquals(expected, string.replace(r3, "X"));
-assertEquals(5, get_count);
+assertEquals(4, get_count);
 
 
 function testName(name) {