[gedit-plugins] Remove dashboard page from help since plugin was removed on 2019/1/9

[Jordi Mas <jmas src gnome org>]

commit 62d577119247cb88059da4e0b444b1af497a2c99
Author: Jordi Mas <jmas softcatala org>
Date:   Sun May 12 08:02:52 2019 +0200

    Remove dashboard page from help since plugin was removed on 2019/1/9

 help/C/dashboard.page | 58 ---------------------------------------------------
 help/meson.build      |  1 -
 2 files changed, 59 deletions(-)
---
diff --git a/help/meson.build b/help/meson.build
index e7fe938..fe54ce1 100644
--- a/help/meson.build
+++ b/help/meson.build
@@ -5,7 +5,6 @@ gedit_help_sources = [
   'code-comment.page',
   'color-picker.page',
   'commander.page',
-  'dashboard.page',
   'draw-spaces.page',
   'git.page',
   'join-split-lines.page',