Fix failures of vc-find-revision with non-ASCII file names

* lisp/vc/vc.el (vc-find-revision): Instead of binding
coding-system-for-write, make the buffer-file-coding-system of
the temporary buffer be no-conversion.  This avoids the
unwanted side effect of not encoding the command-line
arguments of the VCS commands invoked by the backend.
1 job for emacs-26 in 26 minutes and 14 seconds (queued for 3 seconds)
Status Job ID Name Coverage
passed #756