gnu: ruby-protobuf: Fix build.

* gnu/packages/protobuf.scm (ruby-protobuf)[arguments]: Update style.
[native-inputs]: Remove ruby-pry-byebug.

gnu/packages/protobuf.scm

@@ -563,8 +563,9 @@ source files.")
                 "12hp1clg83jfl35x1h2ymzpj5w83wrnqw7hjfc6mqa8lsvpw535r"))))
     (build-system ruby-build-system)
     (arguments
-     `(#:phases
-       (modify-phases %standard-phases
+     (list
+      #:phases
+      #~(modify-phases %standard-phases
           (add-after 'unpack 'do-not-use-bundler-for-tests
             (lambda _
               (substitute* "spec/spec_helper.rb"
@@ -605,7 +606,6 @@ source files.")
      (list ruby-benchmark-ips
            ruby-ffi-rzmq
            ruby-parser
-           ruby-pry-byebug
            ruby-pry-stack-explorer
            ruby-rake
            ruby-rspec