Use Sourcegraph v0.0.21 instead of v0.0.22

**Why?**
https://gitlab.com/gitlab-org/gitlab/merge_requests/23035#note_275371962

package.json

@@ -43,7 +43,7 @@
     "@gitlab/ui": "^8.18.0",
     "@gitlab/visual-review-tools": "1.5.1",
     "@sentry/browser": "^5.10.2",
-    "@sourcegraph/code-host-integration": "^0.0.22",
+    "@sourcegraph/code-host-integration": "0.0.21",
     "apollo-cache-inmemory": "^1.6.3",
     "apollo-client": "^2.6.4",
     "apollo-link": "^1.2.11",

yarn.lock

@@ -986,10 +986,10 @@
     "@sentry/types" "5.10.0"
     tslib "^1.9.3"
 
-"@sourcegraph/code-host-integration@^0.0.22":
-  version "0.0.22"
-  resolved "https://registry.yarnpkg.com/@sourcegraph/code-host-integration/-/code-host-integration-0.0.22.tgz#e292714bc758ce38285fbf1b2791425ccaea8304"
-  integrity sha512-tpS2KPWwu+IfgFoWrNpcc2Pw7N2OI7RLHoo/pbvW3PB57gMTBmcOvNpTaP/Ptol2SY22bNjp5cLZ1SFPVfRnkg==
+"@sourcegraph/code-host-integration@0.0.21":
+  version "0.0.21"
+  resolved "https://registry.yarnpkg.com/@sourcegraph/code-host-integration/-/code-host-integration-0.0.21.tgz#d536ccb3d9fda6d0c9d611ed6b80813265d8cb2f"
+  integrity sha512-HRBb6FO5+kc0JM6mAzhBGrDCuMdkGBjgdnKGnkW8B/FFKEtZEB6HI4ghGfY0eH01tFRis7snkZ4b3NSLjAbHew==
 
 "@types/anymatch@*":
   version "1.3.0"