Update runtime files

runtime/indent/cobol.vim

@@ -7,6 +7,7 @@
 " Ankit Jain      22.03.2019     Changes & fixes:
 "                                Allow chars in 1st 6 columns
 "                                #C22032019
+" Ankit Jain      24.09.2021     add b:undo_indent (request by tpope)
 
 if exists("b:did_indent")
     finish
@@ -18,6 +19,8 @@ setlocal indentexpr=GetCobolIndent(v:lnum)
 setlocal indentkeys&
 setlocal indentkeys+=0<*>,0/,0$,0=01,=~division,=~section,0=~end,0=~then,0=~else,0=~when,*<Return>,.
 
+let b:undo_indent = "setlocal expandtab< indentexpr< indentkeys<"
+
 " Only define the function once.
 if exists("*GetCobolIndent")
     finish