patch 8.1.0858: 'indentkeys' and 'cinkeys' defaults are different

Problem:    'indentkeys' and 'cinkeys' defaults are different.
Solution:   Make them the same, update docs. (close #3882)
diff --git a/runtime/doc/indent.txt b/runtime/doc/indent.txt
index 2c12fe4..299d1ac 100644
--- a/runtime/doc/indent.txt
+++ b/runtime/doc/indent.txt
@@ -60,12 +60,13 @@
 only triggers C-indenting.  When 'indentexpr' is not empty 'indentkeys' is
 used instead.  The format of 'cinkeys' and 'indentkeys' is equal.
 
-The default is "0{,0},0),:,0#,!^F,o,O,e" which specifies that indenting occurs
-as follows:
+The default is "0{,0},0),0],:,0#,!^F,o,O,e" which specifies that indenting
+occurs as follows:
 
 	"0{"	if you type '{' as the first character in a line
 	"0}"	if you type '}' as the first character in a line
 	"0)"	if you type ')' as the first character in a line
+	"0]"	if you type ']' as the first character in a line
 	":"	if you type ':' after a label or case statement
 	"0#"	if you type '#' as the first character in a line
 	"!^F"	if you type CTRL-F (which is not inserted)