fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-REXML-6861566

Gemfile

@@ -84,7 +84,7 @@ end
 
 group :test do
   gem 'minitest-stub_any_instance'
-  gem 'webmock'
+  gem 'webmock', '>= 3.23.1'
 end
 
 group :production do

Gemfile.lock

@@ -107,7 +107,7 @@ GEM
       babel-source (>= 4.0, < 6)
       execjs (~> 2.0)
     base64 (0.2.0)
-    bigdecimal (3.1.7)
+    bigdecimal (3.1.8)
     bindata (2.5.0)
     bindex (0.8.1)
     bootstrap (4.6.2)
@@ -266,7 +266,7 @@ GEM
     popper_js (1.16.1)
     psych (5.1.2)
       stringio
-    public_suffix (5.0.4)
+    public_suffix (5.0.5)
     puma (6.4.2)
       nio4r (~> 2.0)
     racc (1.7.3)
@@ -321,7 +321,8 @@ GEM
     repost (0.3.8)
     request_store (1.6.0)
       rack (>= 1.4)
-    rexml (3.2.6)
+    rexml (3.2.8)
+      strscan (>= 3.0.9)
     rspec (3.13.0)
       rspec-core (~> 3.13.0)
       rspec-expectations (~> 3.13.0)
@@ -391,6 +392,7 @@ GEM
       activesupport (>= 5.2)
       sprockets (>= 3.0.0)
     stringio (3.1.0)
+    strscan (3.1.0)
     sync (0.5.0)
     syslog_protocol (0.9.2)
     term-ansicolor (1.7.2)
@@ -415,7 +417,7 @@ GEM
       activemodel (>= 6.0.0)
       bindex (>= 0.4.0)
       railties (>= 6.0.0)
-    webmock (3.23.0)
+    webmock (3.23.1)
       addressable (>= 2.8.0)
       crack (>= 0.3.2)
       hashdiff (>= 0.4.0, < 2.0.0)
@@ -473,4 +475,7 @@ DEPENDENCIES
   turbolinks (~> 5)
   tzinfo-data
   web-console (>= 4.2.1)
-  webmock
+  webmock (>= 3.23.1)
+
+BUNDLED WITH
+   2.1.4