Keep Core Location flag until 88

While Core Location should be shipped by 88 it is useful to keep the
flag so that I can have the flag on ToT while working on launch and I
can make bug fixes along the way.

Bug: 1051591
Change-Id: Ie2acd0406c5801009380d3fe5c54ea666cddbca9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2380674Reviewed-by: Matt Reynolds <mattreynolds@chromium.org>
Commit-Queue: James Hollyer <jameshollyer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803248}

chrome/browser/flag-metadata.json

@@ -1297,7 +1297,7 @@
   {
     "name": "enable-core-location-implementation",
     "owners": [ "jameshollyer@google.com" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 88
   },
   {
     "name": "enable-credit-card-assist",