Revert "gnu: Add guile3.0-commonmark."

This reverts commit 346386f3f7.

A Guile 3.0 variant had already been added with commit
1fa3423236.

gnu/packages/guile-xyz.scm

@@ -2090,15 +2090,6 @@ key-value cache and store.")
                      "3.0 2.2 2.0"))
                   #t))))
     (build-system gnu-build-system)
-    (arguments
-     `(#:phases
-       (modify-phases %standard-phases
-         (add-after 'unpack 'support-guile-3.0
-           (lambda _
-             (substitute* "configure"
-               (("_guile_versions_to_search=\"2.2")
-                "_guile_versions_to_search=\"3.0 2.2"))
-             #t)))))
     (inputs
      `(("guile" ,guile-2.2)))
     (native-inputs
@@ -2125,12 +2116,6 @@ is no support for parsing block and inline level HTML.")
     (name "guile2.0-commonmark")
     (inputs `(("guile" ,guile-2.0)))))
 
-(define-public guile3.0-commonmark
-  (package
-    (inherit guile-commonmark)
-    (name "guile3.0-commonmark")
-    (inputs `(("guile" ,guile-3.0)))))
-
 (define-public mcron
   (package
     (name "mcron")