gnu: wxmaxima: Update to 18.10.1.

* gnu/packages/maths.scm (wxmaxima): Update to 18.10.1.
[source]: Update URL and remove patch.
* gnu/packages/patches/wxmaxima-do-not-use-old-gnuplot-parameters.patch: Remove
file.
* gnu/local.mk (dist_patch_DATA): Remove patch.

gnu/packages/patches/wxmaxima-do-not-use-old-gnuplot-parameters.patch

@@ -1,26 +0,0 @@
-This fixes the wxplot2d plotting issue found at
-https://github.com/andrejv/wxmaxima/issues/973.
-
-From 5a0693c97ceaa4935b908f1e478126896952f399 Mon Sep 17 00:00:00 2001
-From: =?UTF-8?q?Gunter=20K=C3=B6nigsmann?= <gunter@peterpall.de>
-Date: Mon, 19 Feb 2018 05:37:35 +0100
-Subject: [PATCH] Seems I accidentally made wxMaxima to default to parameters
- for old gnuplots. Resolves #973
-
----
- data/wxmathml.lisp.in | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-diff --git a/data/wxmathml.lisp.in b/data/wxmathml.lisp.in
-index a32e3fc3..4e19acaf 100644
---- a/data/wxmathml.lisp.in
-+++ b/data/wxmathml.lisp.in
-@@ -43,7 +43,7 @@
- (defvar $wxsubscripts t
-   "Recognize TeX-style subscripts")
- (defvar $wxplot_pngcairo nil "Use gnuplot's pngcairo terminal for new plots?")
--(defmvar $wxplot_old_gnuplot t)
-+(defmvar $wxplot_old_gnuplot nil)
- 
- (defun $wxstatusbar (status)
-   (format t "<statusbar>~a</statusbar>~%" status))