Upgrade metrics-sharelatex to 2.6.2

This version fixes the HTTP request timing metrics, which were not
reporting correctly.

services/docstore/package.json

@@ -23,7 +23,7 @@
     "body-parser": "^1.19.0",
     "express": "^4.17.1",
     "logger-sharelatex": "^1.9.0",
-    "metrics-sharelatex": "^2.6.1",
+    "metrics-sharelatex": "^2.6.2",
     "mongojs": "3.1.0",
     "settings-sharelatex": "^1.1.0",
     "underscore": "~1.9.2"