Be more explicit about the lack of X11 integration

I don't want anyone getting the idea that the `-X` flag they might have
used has anything to do with why the `+` is working for them

src/nvim/main.c

@@ -935,9 +935,6 @@ static void command_line_scan(mparm_T *parmp)
           want_argument = TRUE;
           break;
 
-        case 'X':                 /* "-X"  don't connect to X server */
-          break;
-
         case 'Z':                 /* "-Z"  restricted mode */
           restricted = TRUE;
           break;

src/nvim/po/CMakeLists.txt

@@ -82,7 +82,7 @@ if(HAVE_WORKING_LIBINTL AND GETTEXT_FOUND AND XGETTEXT_PRG AND ICONV_PRG)
     set(poFile ${CMAKE_CURRENT_SOURCE_DIR}/${name}.po)
 
     add_custom_target(check-po-${name}
-      COMMAND $<TARGET_FILE:nvim> -u NONE -n -e -X
+      COMMAND $<TARGET_FILE:nvim> -u NONE -n -e
           -S ${CMAKE_CURRENT_SOURCE_DIR}/check.vim
           -c "if error == 0 | q | endif" -c cq ${poFile} ||
           ${CMAKE_COMMAND} -E echo "${name}.po failed the check."

src/nvim/testdir/test49.vim

@@ -456,7 +456,7 @@ function! ExtraVim(...)
     " messing up the user's viminfo file.
     let redirect = a:0 ?
 	\ " -c 'au VimLeave * redir END' -c 'redir\\! >" . a:1 . "'" : ""
-    exec "!echo '" . debug_quits . "q' | ../../../build/bin/nvim -u NONE -N -Xes" . redirect .
+    exec "!echo '" . debug_quits . "q' | ../../../build/bin/nvim -u NONE -N -es" . redirect .
 	\ " -c 'debuggreedy|set viminfo+=nviminfo'" .
 	\ " -c 'let ExtraVimBegin = " . extra_begin . "'" .
 	\ " -c 'let ExtraVimResult = \"" . resultfile . "\"'" . breakpoints .