Update runtime files

runtime/indent/dtd.vim

@@ -4,6 +4,12 @@
 " Previous Maintainer:	Nikolai Weibull <now@bitwi.se>
 " Last Change:		24 Sep 2021
 
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+  finish
+endif
+let b:did_indent = 1
+
 setlocal indentexpr=GetDTDIndent()
 setlocal indentkeys=!^F,o,O,>
 setlocal nosmartindent