Remove redundant notes about arch:all packages

In an architecture only migration, we currently see two notes for
every arch:all packages:

 * Ignoring "new" arch:all package
 * Ignoring "removal" of arch:all package

But a closer look at the situation is that the arch:all packages is
generally the same in both testing and the source suite.

This commit removes these notes when the arch:all is the same in both
suites.

Signed-off-by: Niels Thykier <niels@thykier.net>

britney.py

@@ -1058,6 +1058,8 @@ class Britney(object):
 
             # if the new binary package is architecture-independent, then skip it
             if binary_u[ARCHITECTURE] == 'all':
+                if pkg_id not in source_t[BINARIES]:
+                    # only add a note if the arch:all does not match the expected version
                     excuse.addhtml("Ignoring %s %s (from %s) as it is arch: all" % (pkg_name, binary_u[VERSION], pkgsv))
                 continue
 
@@ -1127,6 +1129,8 @@ class Britney(object):
                     # if the package is architecture-independent, then ignore it
                     tpkg_data = packages_t_a[pkg]
                     if tpkg_data[ARCHITECTURE] == 'all':
+                        if pkg_id not in source_u[BINARIES]:
+                            # only add a note if the arch:all does not match the expected version
                             excuse.addhtml("Ignoring removal of %s as it is arch: all" % (pkg))
                         continue
                     # if the package is not produced by the new source package, then remove it from testing