patch 9.1.0899: default for 'backspace' can be set in C code

Problem:  default for 'backspace' can be set in C code
Solution: promote the default for 'backspace' from defaults.vim to the C
          code (Luca Saccarola)

closes: #16143

Signed-off-by: Luca Saccarola <github.e41mv@aleeas.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/doc/version9.txt b/runtime/doc/version9.txt
index b9977a9..2aadcd3 100644
--- a/runtime/doc/version9.txt
+++ b/runtime/doc/version9.txt
@@ -41611,6 +41611,8 @@
 - 'rulerformat' now supports the |stl-%!| item
 - the default 'history' option value has been increased to 200 and removed
   from |defaults.vim|
+- the default 'backspace' option for Vim has been set to "indent,eol,start"
+  and removed from |defaults.vim|
 
 							*added-9.2*
 Added ~