translation(sr): Update Serbian messages (#14143)

* translation(sr): Update Serbian messages
* Update serbian.nsi
* Update gvim.nsi

Add serbian language to the installer

Signed-off-by: Ivan Pešić <27575106+eevan78@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/nsis/lang/serbian.nsi b/nsis/lang/serbian.nsi
index 9912ec5..11d889a 100644
--- a/nsis/lang/serbian.nsi
+++ b/nsis/lang/serbian.nsi
@@ -6,7 +6,7 @@
 # fileencoding : UTF-8
 # Author       : Ivan Pešić
 
-!insertmacro MUI_LANGUAGE "Српски"
+!insertmacro MUI_LANGUAGE "Serbian"
 
 
 # Overwrite the default translation.