gnu: python2-matplotlib: Do not inherit test adjustments.

This is a follow-up to commit 9e7cb2f1e1.

* gnu/packages/python-xyz.scm (python2-matplotlib)[arguments]: Do not inherit
the 'fix-and-disable-failing-tests' phase.

gnu/packages/python-xyz.scm

@@ -4147,6 +4147,7 @@ (define-public python2-matplotlib
                            (assoc-ref inputs "jquery-ui")
                            "-d" dir))
                  #t))
+             (delete 'fix-and-disable-failing-tests)
              (delete 'check))))) ; These tests weren't run the the past.
       ;; Make sure to use special packages for Python 2 instead
       ;; of those automatically rewritten by package-with-python2.