Extend expiration for WebAssembly flags

Extending flag expiration milestones for WebAssembly features that are
still in use by a year.

Status of features gated by flags:
* code caching - Enabled by default, okay to expire.
* baseline/tiering  - Ongoing finch trial
* lazy compilation - Lazy compilation is still experimental
* threads - Enabled by default in chrome, waiting on other browsers for
complete implementations, so still useful for testing
* simd - Still experimental, used for prototyping and gathering
performance data.

Change-Id: I51ae98b3dd784b1d619cebf15f81252c697f62a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2158037Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#761037}

chrome/browser/flag-metadata.json

@@ -2213,7 +2213,7 @@
   {
     "name": "enable-webassembly-baseline",
     "owners": [ "clemensb", "wasm-team@google.com" ],
-    "expiry_milestone": 83
+    "expiry_milestone": 92
   },
   {
     "name": "enable-webassembly-code-cache",
@@ -2223,22 +2223,22 @@
   {
     "name": "enable-webassembly-lazy-compilation",
     "owners": [ "clemensb", "wasm-team@google.com" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 92
   },
   {
     "name": "enable-webassembly-simd",
     "owners": [ "gdeepti", "wasm-team@google.com" ],
-    "expiry_milestone": 83
+    "expiry_milestone": 92
   },
   {
     "name": "enable-webassembly-threads",
     "owners": [ "binji", "hablich", "wasm-team@google.com" ],
-    "expiry_milestone": 83
+    "expiry_milestone": 92
   },
   {
     "name": "enable-webassembly-tiering",
     "owners": [ "clemensb", "wasm-team@google.com" ],
-    "expiry_milestone": 86
+    "expiry_milestone": 92
   },
   {
     "name": "enable-webgl-draft-extensions",