Upgrade acts-on-taggable to v7.0.0

This eliminates the Ruby 2.7 kwargs warning and adds support for Rails
6.1.

CHANGELOG:
https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md

Diff:
https://github.com/mbleigh/acts-as-taggable-on/compare/v6.5.0..v7.0.0

Gemfile

@@ -192,7 +192,7 @@ end
 gem 'state_machines-activerecord', '~> 0.8.0'
 
 # Issue tags
-gem 'acts-as-taggable-on', '~> 6.0'
+gem 'acts-as-taggable-on', '~> 7.0'
 
 # Background jobs
 gem 'sidekiq', '~> 5.2.7'

Gemfile.lock

@@ -63,8 +63,8 @@ GEM
       minitest (~> 5.1)
       tzinfo (~> 1.1)
       zeitwerk (~> 2.2, >= 2.2.2)
-    acts-as-taggable-on (6.5.0)
-      activerecord (>= 5.0, < 6.1)
+    acts-as-taggable-on (7.0.0)
+      activerecord (>= 5.0, < 6.2)
     adamantium (0.2.0)
       ice_nine (~> 0.11.0)
       memoizable (~> 0.4.0)
@@ -1270,7 +1270,7 @@ DEPENDENCIES
   RedCloth (~> 4.3.2)
   acme-client (~> 2.0, >= 2.0.6)
   activerecord-explain-analyze (~> 0.1)
-  acts-as-taggable-on (~> 6.0)
+  acts-as-taggable-on (~> 7.0)
   addressable (~> 2.7)
   akismet (~> 3.0)
   apollo_upload_server (~> 2.0.2)