Don't print :__pkg__ for package rules, since that's the default.

To reduce clutter a little.

// Added for rvc-dev. Used this bug as it is the bug that needs all the build changes.
Bug: 155164730

Test: m nothing
Merged-In: I0d2d86f00c3d38e603d6f58c4b1dd9a4170bf819
Change-Id: I0d2d86f00c3d38e603d6f58c4b1dd9a4170bf819
(cherry picked from commit 01407c52)