gnu: texlive: Fix bug recently introduced in d4bf49b1.

Fixes bug introduced in d4bf49b1.

* gnu/packages/texlive.scm (texlive): Change 'alist-replace' to
  'alist-cons-before'.

gnu/packages/texlive.scm

@@ -115,7 +115,7 @@ (define-public texlive
          "--with-system-zlib"
          "--with-system-zziplib")
       #:phases
-       (alist-replace
+       (alist-cons-before
         'configure 'patch-perl-shebang
         (lambda _
           (substitute* "utils/psutils/Makefile.in"