gnu: Remove expat/fixed.

The merge preceding this commit (fb9a23a3f3) ignored the replacement added in
5a836ce38c (gnu: expat: fix CVE-2018-20843), because the fix is already
present in Expat 2.2.7.  This commit removes the remaining bits.

* gnu/packages/patches/expat-CVE-2018-20843.patch: Delete file.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/xml.scm (expat/fixed): Remove variable.

gnu/local.mk

@@ -781,7 +781,6 @@ dist_patch_DATA =						\
   %D%/packages/patches/evilwm-lost-focus-bug.patch		\
   %D%/packages/patches/exiv2-CVE-2017-14860.patch		\
   %D%/packages/patches/exiv2-CVE-2017-14859-14862-14864.patch	\
-  %D%/packages/patches/expat-CVE-2018-20843.patch		\
   %D%/packages/patches/extundelete-e2fsprogs-1.44.patch		\
   %D%/packages/patches/fastcap-mulGlobal.patch			\
   %D%/packages/patches/fastcap-mulSetup.patch			\

gnu/packages/patches/expat-CVE-2018-20843.patch

@@ -1,21 +0,0 @@
-Fix extraction of namespace prefix from XML name.
-Fixes CVE-2018-20843
-
-This patch comes from upstream commit 11f8838bf99ea0a6f0b76f9760c43704d00c4ff6
-https://github.com/libexpat/libexpat/commit/11f8838bf99ea0a6f0b76f9760c43704d00c4ff6
-
-CVE is https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20843
-
-diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c
-index 30d55c5..737d7cd 100644
---- a/lib/xmlparse.c
-+++ b/lib/xmlparse.c
-@@ -6071,7 +6071,7 @@ setElementTypePrefix(XML_Parser parser, ELEMENT_TYPE *elementType)
-       else
-         poolDiscard(&dtd->pool);
-       elementType->prefix = prefix;
--
-+      break;
-     }
-   }
-   return 1;

gnu/packages/xml.scm

@@ -88,14 +88,6 @@ stream-oriented parser in which an application registers handlers for
 things the parser might find in the XML document (like start tags).")
     (license license:expat)))
 
-(define expat/fixed
-  (package
-    (inherit expat)
-    (source
-     (origin
-       (inherit (package-source expat))
-       (patches (search-patches "expat-CVE-2018-20843.patch"))))))
-
 (define-public libebml
   (package
     (name "libebml")