gnu: ruby-gem-hadar: Use git-minimal/pinned.

This helps reduce the dependencies on git, as I think it's find to build
ruby-gem-hadar with a slightly older git, at least during periods when
git-minimal/pinned needs updating.

* gnu/packages/ruby.scm (ruby-gem-hadar)[propagated-inputs]: Use
git-minimal/pinned.

Change-Id: I48e7725f8e4956f1a8311df1867d8d441c5cb4c2

gnu/packages/ruby.scm

@@ -7817,7 +7817,7 @@ documentation for Ruby code.")
           (lambda _
             (invoke "gem" "build" "gem_hadar.gemspec"))))))
     (propagated-inputs
-     (list git ruby-tins ruby-yard))
+     (list git-minimal/pinned ruby-tins ruby-yard))
     (synopsis "Library for the development of Ruby gems")
     (description
      "This library contains some useful functionality to support the