patch 8.0.0304: assign test fails in the GUI

Problem:    Assign test fails in the GUI.
Solution:   Skip the test for setting t_k1.

Author: brammool

src/testdir/test_assign.vim

@@ -15,11 +15,13 @@ func Test_let_termcap()
   call assert_match('t_te.*^[[yes;', execute("set termcap"))
   let &t_te = old_t_te
 
-  " Key code
-  let old_t_k1 = &t_k1
-  let &t_k1 = "that"
-  call assert_match('t_k1.*that', execute("set termcap"))
-  let &t_k1 = old_t_k1
+  if !has('gui_running')
+    " Key code
+    let old_t_k1 = &t_k1
+    let &t_k1 = "that"
+    call assert_match('t_k1.*that', execute("set termcap"))
+    let &t_k1 = old_t_k1
+  endif
 
   call assert_fails('let x = &t_xx', 'E15')
   let &t_xx = "yes"

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    304,
 /**/
     303,
 /**/