chore: Set the license, remove redundant metadata.

Author: schwern

time_range.gemspec

@@ -13,8 +13,8 @@ Gem::Specification.new do |spec|
   spec.homepage = "https://github.com/schwern/ruby-time_range"
   spec.required_ruby_version = ">= 2.7"
 
-  spec.metadata["homepage_uri"] = spec.homepage
-  spec.metadata["source_code_uri"] = "https://github.com/schwern/ruby-time_range"
+  spec.licenses = ["MIT"]
+  spec.metadata["source_code_uri"] = spec.homepage
 
   # Specify which files should be added to the gem when it is released.
   # The `git ls-files -z` loads the files in the RubyGem that have been added into git.