Use Ruby 2.7 as a minimum version

Summary: We now consider Ruby 2.7 the minimum supported version.

Differential Revision: D65913794

fbshipit-source-id: 12c8704324cc75cd114eb18ee532ca42e03dc0fc

.rubocop.yml

@@ -1,6 +1,6 @@
 AllCops:
   DisabledByDefault: true
-  TargetRubyVersion: 2.5
+  TargetRubyVersion: 2.7
   Exclude:
     # template files named `rb` instead of `erb` are a sin against ruby-nature.
     - '**/templates/**/*.rb'#
@@ -1260,8 +1260,9 @@ Style/SingleLineBlockParams:
 Style/SingleLineMethods:
   Enabled: true
 
+# TODO ratchet in a separate diff
 Style/SlicingWithRange:
-  Enabled: true
+  Enabled: false
 
 # TODO re-evaluate after chef-workstation upgrade
 Style/SoleNestedConditional: