chore(deps-dev): bump webmock in /fluent-plugin-events (#608)

Bumps [webmock](https://github.com/bblimke/webmock) from 3.19.1 to 3.20.0.
- [Changelog](https://github.com/bblimke/webmock/blob/master/CHANGELOG.md)
- [Commits](bblimke/webmock@v3.19.1...v3.20.0)

---
updated-dependencies:
- dependency-name: webmock
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

fluent-plugin-events/Gemfile.lock

@@ -19,12 +19,14 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.8.5)
+    addressable (2.8.6)
       public_suffix (>= 2.0.2, < 6.0)
+    bigdecimal (3.1.6)
     concurrent-ruby (1.1.10)
     connection_pool (2.4.0)
     cool.io (1.7.1)
-    crack (0.4.5)
+    crack (0.4.6)
+      bigdecimal
       rexml
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
@@ -69,7 +71,7 @@ GEM
       tzinfo-data (~> 1.0)
       webrick (~> 1.4)
       yajl-ruby (~> 1.0)
-    hashdiff (1.0.1)
+    hashdiff (1.1.0)
     http (4.4.1)
       addressable (~> 2.3)
       http-cookie (~> 1.0)
@@ -88,7 +90,7 @@ GEM
     net-http-persistent (4.0.2)
       connection_pool (~> 2.2)
     power_assert (2.0.3)
-    public_suffix (5.0.3)
+    public_suffix (5.0.4)
     rake (13.1.0)
     recursive-open-struct (1.1.3)
     rexml (3.2.6)
@@ -106,7 +108,7 @@ GEM
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.8.2)
-    webmock (3.19.1)
+    webmock (3.20.0)
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)