gnu: r-biocinstaller: Remove entirely.

This follows up on commit 0971f8bd88,
which led to ‘r-biocmanager: unbound variable’ errors.  See
<https://lists.gnu.org/archive/html/guix-devel/2019-07/msg00120.html>.

* gnu/packages/bioinformatics.scm (r-biocinstaller): Remove variable.

gnu/packages/bioinformatics.scm

@@ -7237,9 +7237,6 @@ BLAST, KEGG, GenBank, MEDLINE and GO.")
     ;; (LGPLv2.1+) and scripts in samples (which have GPL2 and GPL2+)
     (license (list license:ruby license:lgpl2.1+ license:gpl2+ ))))
 
-(define-public r-biocinstaller
-  (deprecated-package "r-biocinstaller" r-biocmanager))
-
 (define-public r-biocviews
   (package
     (name "r-biocviews")