Use latest WebMock, 3.19.1

I thought this might help with an issue I'm experiencing where there the
uri of a stubbed response is unexpectedly nil, but it did not.

Author: mokagio

Gemfile.lock

@@ -29,7 +29,7 @@ GEM
       i18n (>= 1.6, < 2)
       minitest (>= 5.1)
       tzinfo (~> 2.0)
-    addressable (2.8.4)
+    addressable (2.8.5)
       public_suffix (>= 2.0.2, < 6.0)
     algoliasearch (1.27.5)
       httpclient (~> 2.8, >= 2.8.3)
@@ -320,7 +320,7 @@ GEM
       trailblazer-option (>= 0.1.1, < 0.2.0)
       uber (< 0.2.0)
     retriable (3.1.2)
-    rexml (3.2.5)
+    rexml (3.2.6)
     rmagick (4.3.0)
     rouge (2.0.7)
     rspec (3.12.0)
@@ -392,7 +392,7 @@ GEM
       unf_ext
     unf_ext (0.0.8.2)
     unicode-display_width (2.4.2)
-    webmock (3.18.1)
+    webmock (3.19.1)
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)