Rely on automated tarball inspection

Since ff9ff26 the tarballs are
inspected automatically, which verifies they are valid tar files and not
some garbage. By now we can rely on this and no longer need the manual
inspection using file-roller.

inspect_tarballs

@@ -14,4 +14,3 @@ for project in $TAR_PROJECTS ; do
 		exit 1
 	fi
 done
-file-roller "${filenames[@]}"