[gimp/gimp-2-8] Fix typos in 2.8.20 NEWS

[Michael Schumacher <schumaml src gnome org>]

commit 9519d698d80e57fc57b7bd99600f9e6b9ecee064
Author: Michael Schumacher <schumaml gmx de>
Date:   Fri Feb 3 11:39:57 2017 +0100

    Fix typos in 2.8.20 NEWS
    
    Note to self: do not write release news late at night during a developer meeting.

 NEWS |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/NEWS b/NEWS
index c5e3cd1..a2364c1 100644
--- a/NEWS
+++ b/NEWS
@@ -32,7 +32,7 @@ GUI:
    multi-window-mode
  - Disable the new "automatic window tabbing" feature introduced on macOS
    Sierra
- - Improve the visiblity of slider handles with dark themes
+ - Improve the visibility of slider handles with dark themes
  - Make it harder to switch to renaming if selecting already selected
    items in resource lists
 
@@ -52,7 +52,7 @@ Windows Installer:
  - Reduce the memory requirement when running the installer (has
    already been shipped in a 2.8.18 installer-only update)
  - Ship an updated libcairo to fix GTK+ UI rendering problems, like
-   missing palette border/bevel and shadowa under tab labels
+   missing palette border/bevel and shadows under tab labels
 
 
 macOS DMG:
@@ -75,8 +75,8 @@ Plug-ins:
  - mkgen.pl: fix calls to write_file() routine to write to current
    directory
  - When printing, the images are composed onto a white background to
-   prevent printing a black box instead of a transaprent image
- - Fix color visison deficiency display filters to apply gamma
+   prevent printing a black box instead of a transparent image
+ - Fix color vision deficiency display filters to apply gamma
    correction directly