fix: Gemfile & Gemfile.lock to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-RUBY-RAKE-552000

Gemfile

@@ -26,5 +26,5 @@ group :development do
   gem 'launchy'
   gem 'pry'
   gem 'rerun'
-  gem 'rake'
+  gem 'rake', '>= 12.3.3'
 end

Gemfile.lock

@@ -70,7 +70,7 @@ GEM
       rack
     rack-test (0.7.0)
       rack (>= 1.0, < 3)
-    rake (12.1.0)
+    rake (13.0.1)
     rb-fsevent (0.10.2)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
@@ -140,7 +140,7 @@ DEPENDENCIES
   launchy
   poltergeist
   pry
-  rake
+  rake (>= 12.3.3)
   rerun
   rspec
   sinatra
@@ -153,4 +153,4 @@ DEPENDENCIES
   validate_url
 
 BUNDLED WITH
-   1.15.3
+   1.17.3