[patch] README: remove references to deleted remote-*.c

[Andrew Cagney]

> This patch removes gdb/README references to deleted remote-*.c files.
> All these files are deleted, not just obsolete.
> 
> I noticed this while I was writing new text for the next section down,
> "Reporting Bugs in GDB".

Michael, check the bug database for some additional state on this.  The 
`correct fix' involves an addition to the documentation.

Andrew