debian/implicit: skip unnecessary removal of $pkg.deb*

debian/implicit: skip unnecessary removal of $pkg.deb*

The rules to build foo.deb and foo.udeb remove various files named
after the implicit prerequisites after following rules to build those
same files.  Presumably this is intended to prevent real files that
happen to be around from preventing the rules from being run, but the
removal takes place after dependencies have been satisfied so it has
no useful effect.

Eliminate the removal for clarity.

In the future these could be made prerequisites of the .PHONY
pseudotarget using an appropriate $(wildcard) expression to actually
ensure poorly named files could not interfere with GNU make's
dependency management.  Luckily it hasn't been a problem in practice.
This patch doesn't do anything in that direction.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>