gnu: wxmaxima: Update to 18.11.4.

* gnu/packages/maths.scm (wxmaxima): Update to 18.11.4.
[source]: Switch to git-fetch.

gnu/packages/maths.scm

@@ -2848,16 +2848,17 @@ point numbers.")
 (define-public wxmaxima
   (package
     (name "wxmaxima")
-    (version "18.10.1")
+    (version "18.11.4")
     (source
      (origin
-       (method url-fetch)
-       (uri (string-append "https://github.com/wxMaxima-developers/" name
-                           "/archive/Version-" version ".tar.gz"))
-       (file-name (string-append name "-" version ".tar.gz"))
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/wxMaxima-developers/wxmaxima.git")
+             (commit (string-append "Version-" version))))
+       (file-name (git-file-name name version))
        (sha256
         (base32
-         "0c2blq65r0am509p3rjqpwqk6vl5r2yg1p9nh2jczf80vhi3ldas"))))
+         "1sz8n9v23q442l7yjj67pjh0dk78rl4cbcc3j8m1bm88anlfxl9r"))))
     (build-system cmake-build-system)
     (native-inputs
      `(("gettext" ,gettext-minimal)))