Bump mocha from 2.3.0 to 2.7.1 (#3553)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Gemfile.lock

@@ -143,7 +143,7 @@ GEM
     mini_mime (1.1.5)
     mini_portile2 (2.8.8)
     minitest (5.25.5)
-    mocha (2.3.0)
+    mocha (2.7.1)
       ruby2_keywords (>= 0.0.5)
     msgpack (1.8.0)
     mutex_m (0.3.0)