fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-REXML-7462086

Gemfile

@@ -1,5 +1,5 @@
 source "https://rubygems.org"
 
 group :test do
-  gem "rubocop"
+  gem "rubocop", ">= 0.86.0"
 end

Gemfile.lock

@@ -1,29 +1,40 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    ast (2.4.0)
-    parallel (1.19.1)
-    parser (2.7.1.3)
-      ast (~> 2.4.0)
-    rainbow (3.0.0)
-    regexp_parser (1.7.1)
-    rexml (3.2.4)
-    rubocop (0.85.1)
+    ast (2.4.2)
+    json (2.7.2)
+    language_server-protocol (3.17.0.3)
+    parallel (1.25.1)
+    parser (3.3.4.0)
+      ast (~> 2.4.1)
+      racc
+    racc (1.8.0)
+    rainbow (3.1.1)
+    regexp_parser (2.9.2)
+    rexml (3.3.2)
+      strscan
+    rubocop (1.65.0)
+      json (~> 2.3)
+      language_server-protocol (>= 3.17.0)
       parallel (~> 1.10)
-      parser (>= 2.7.0.1)
+      parser (>= 3.3.0.2)
       rainbow (>= 2.2.2, < 4.0)
-      regexp_parser (>= 1.7)
-      rexml
-      rubocop-ast (>= 0.0.3)
+      regexp_parser (>= 2.4, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 1.4.0, < 2.0)
-    rubocop-ast (0.0.3)
-      parser (>= 2.7.0.1)
-    ruby-progressbar (1.10.1)
-    unicode-display_width (1.7.0)
+      unicode-display_width (>= 2.4.0, < 3.0)
+    rubocop-ast (1.31.3)
+      parser (>= 3.3.1.0)
+    ruby-progressbar (1.13.0)
+    strscan (3.1.0)
+    unicode-display_width (2.5.0)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
-  rubocop
+  rubocop (>= 0.86.0)
+
+BUNDLED WITH
+   2.1.4