tests: Bump ruby to 3.1.x

Bumps ruby to ~3.1 now that the latest cf-d-c-t image includes that
version rather than ~2.7.

Also unpins bosh-template since the ruby version compatibility was the
reason it was pinned.

Author: ctlong

Gemfile

@@ -1,9 +1,9 @@
 source 'https://rubygems.org'
 
-ruby '~> 2.7'
+ruby '~> 3.1'
 
 group :development, :test do
-  gem 'bosh-template', '2.2.1'
+  gem 'bosh-template'
   gem 'rspec'
   gem 'rspec-its'
 end

Gemfile.lock

@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    bosh-template (2.2.1)
+    bosh-template (2.4.0)
       semi_semantic (~> 1.2.0)
     diff-lcs (1.5.1)
     rspec (3.13.0)
@@ -26,6 +26,12 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  bosh-template (= 2.2.1)
+  bosh-template
   rspec
   rspec-its
+
+RUBY VERSION
+   ruby 3.1.6p260
+
+BUNDLED WITH
+   2.5.23