gnu: cutadapt: Use ‘modify-phases’ syntax.

* gnu/packages/bioinformatics.scm (cutadapt)[arguments]: Use
‘modify-phases’.

gnu/packages/bioinformatics.scm

@@ -1816,9 +1816,11 @@ preparation protocols.")
                 "19smhh6444ikn4jlmyhvffw4m5aw7yg07rqsk7arg8dkwyga1i4v"))))
     (build-system python-build-system)
     (arguments
-     ;; tests must be run after install
-     `(#:phases (alist-cons-after
-                 'install 'check
+     `(#:phases
+       (modify-phases %standard-phases
+         ;; The tests must be run after installation.
+         (delete 'check)
+         (add-after 'install 'check
            (lambda* (#:key inputs outputs #:allow-other-keys)
              (setenv "PYTHONPATH"
                      (string-append
@@ -1828,8 +1830,7 @@ preparation protocols.")
                       (string-take (string-take-right
                                     (assoc-ref inputs "python") 5) 3)
                       "/site-packages"))
-                   (zero? (system* "nosetests" "-P" "tests")))
-                 (alist-delete 'check %standard-phases))))
+             (zero? (system* "nosetests" "-P" "tests")))))))
     (inputs
      `(("python-xopen" ,python-xopen)))
     (native-inputs