gnu: Remove unused patch 'ocaml-graph-honor-source-date-epoch.patch'.

This is a followup to commit 564cf93f2a.

* gnu/packages/patches/ocaml-graph-honor-source-date-epoch.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.

gnu/local.mk

@@ -1081,7 +1081,6 @@ dist_patch_DATA =						\
   %D%/packages/patches/ocaml-CVE-2015-8869.patch		\
   %D%/packages/patches/ocaml-Add-a-.file-directive.patch	\
   %D%/packages/patches/ocaml-enable-ocamldoc-reproducibility.patch	\
-  %D%/packages/patches/ocaml-graph-honor-source-date-epoch.patch	\
   %D%/packages/patches/omake-fix-non-determinism.patch	\
   %D%/packages/patches/ola-readdir-r.patch			\
   %D%/packages/patches/openbabel-fix-crash-on-nwchem-output.patch	\

gnu/packages/patches/ocaml-graph-honor-source-date-epoch.patch

@@ -1,34 +0,0 @@
-From 354ef78aac0b887fae3c10b28eb2b0d83f66bdfe Mon Sep 17 00:00:00 2001
-From: Julien Lepiller <julien@lepiller.eu>
-Date: Mon, 2 Jan 2017 17:05:24 +0100
-Subject: [PATCH] Honor SOURCE_DATE_EPOCH
-
----
- Makefile.in | 7 ++++++-
- 1 file changed, 6 insertions(+), 1 deletion(-)
-
-diff --git a/Makefile.in b/Makefile.in
-index a32b4b8..ef4c174 100644
---- a/Makefile.in
-+++ b/Makefile.in
-@@ -113,11 +113,16 @@ graph.cmx: $(CMI) $(CMX)
-	$(OCAMLOPT) $(INCLUDES) -pack -o $@ $^
- 
- VERSION=1.8.7
-+ifdef SOURCE_DATE_EPOCH
-+BUILD_DATE=$(shell date -u -d "@$(SOURCE_DATE_EPOCH)" 2>/dev/null || date -u -r "$(SOURCE_DATE_EPOCH)" 2>/dev/null || date)
-+else
-+BUILD_DATE=$(shell date)
-+endif
- 
- src/version.ml: Makefile
-	rm -f $@
-	echo "let version = \""$(VERSION)"\"" > $@
--	echo "let date = \""`date`"\"" >> $@
-+	echo "let date = \""$(BUILD_DATE)"\"" >> $@
- 
- # gtk2 graph editor
- ###################
--- 
-2.11.0
-