[rubygems/rubygems] Use String#unpack1 available since ruby 3.0

https://github.com/rubygems/rubygems/commit/46258d6cb4

lib/bundler/checksum.rb

@@ -43,8 +43,7 @@ module Bundler
         return digest if digest.match?(/\A[0-9a-f]{64}\z/i)
         if digest.match?(%r{\A[-0-9a-z_+/]{43}={0,2}\z}i)
           digest = digest.tr("-_", "+/") # fix urlsafe base64
-          # transform to hex. Use unpack1 when we drop older rubies
+          return digest.unpack1("m0").unpack1("H*")
-          return digest.unpack("m0").first.unpack("H*").first
         end
         raise ArgumentError, "#{digest.inspect} is not a valid SHA256 hex or base64 digest"
       end

lib/bundler/digest.rb

@@ -50,7 +50,7 @@ module Bundler
           words.map!.with_index {|word, index| SHA1_MASK & (word + mutated[index]) }
         end
 
-        words.pack("N*").unpack("H*").first
+        words.pack("N*").unpack1("H*")
       end
 
       private

lib/rubygems/package/old.rb

@@ -70,7 +70,7 @@ class Gem::Package::Old < Gem::Package
           file_data << line
         end
 
-        file_data = file_data.strip.unpack("m")[0]
+        file_data = file_data.strip.unpack1("m")
         file_data = Zlib::Inflate.inflate file_data
 
         raise Gem::Package::FormatError, "#{full_name} in #{@gem} is corrupt" if