runtime(netrw): Decode multibyte percent-encoding filename correctly (#13842)

Use `printf("%c")` instead of `nr2char()` to handle '%xx' as a byte.

Close #13787

Signed-off-by: Ken Takata <kentkt@csc.jp>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/runtime/autoload/netrw.vim b/runtime/autoload/netrw.vim
index 3af7ba0..bcb1f24 100644
--- a/runtime/autoload/netrw.vim
+++ b/runtime/autoload/netrw.vim
@@ -11587,7 +11587,7 @@
 "  netrw#RFC2396: converts %xx into characters {{{2
 fun! netrw#RFC2396(fname)
 "  call Dfunc("netrw#RFC2396(fname<".a:fname.">)")
-  let fname = escape(substitute(a:fname,'%\(\x\x\)','\=nr2char("0x".submatch(1))','ge')," \t")
+  let fname = escape(substitute(a:fname,'%\(\x\x\)','\=printf("%c","0x".submatch(1))','ge')," \t")
 "  call Dret("netrw#RFC2396 ".fname)
   return fname
 endfun