Project: Remove spec.required_ruby_version

It might prevent Dependabot from working properly.

Because rubocop >= 1.51.0 depends on Ruby >= 2.7.0
  and Gemfile depends on rubocop = 1.84.1,
  Ruby >= 2.7.0 is required.
So, because current Ruby version is = 2.5.9,
  version solving has failed.

-- https://github.com/crate/crate_ruby/network/updates/1239572576

The README also says "You will need Ruby 2.0 or greater."

Author: amotl

.rubocop.yml

@@ -4,4 +4,6 @@ require: rubocop-rspec
 
 AllCops:
   NewCops: enable
-  TargetRubyVersion: 2.5
+
+Gemspec/RequiredRubyVersion:
+  Enabled: false

crate_ruby.gemspec

@@ -33,7 +33,6 @@ Gem::Specification.new do |spec|
   spec.description   = 'A Ruby library for the CrateDB HTTP interface with query support, DDL command and schema introspection shortcuts, and support for BLOB tables.'
   spec.homepage      = 'https://crate.io'
   spec.license       = 'Apache-2.0'
-  spec.required_ruby_version = '>= 2.5'
 
   spec.files         = Dir['lib/**/*']
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }