Remove empty cc_library //aos/logging

It was just pointing to //aos/logging:implementations.  Rename that
cc_library to //aos/logging and delete the empty one.  This is an
attempt to simplify //aos/logging.

Change-Id: Ia182d4695f276da96a5c97c017fc2084187ad5d3
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/frc971/control_loops/drivetrain/BUILD b/frc971/control_loops/drivetrain/BUILD
index 454f728..fdbc1dc 100644
--- a/frc971/control_loops/drivetrain/BUILD
+++ b/frc971/control_loops/drivetrain/BUILD
@@ -583,7 +583,7 @@
         ":distance_spline",
         ":spline",
         ":trajectory",
-        "//aos/logging:implementations",
+        "//aos/logging",
         "//aos/network:team_number",
         "//y2020/control_loops/drivetrain:drivetrain_base",
         "@org_tuxfamily_eigen//:eigen",
@@ -694,7 +694,7 @@
     deps = [
         ":distance_spline",
         ":trajectory",
-        "//aos/logging:implementations",
+        "//aos/logging",
         "//aos/network:team_number",
         "//third_party/matplotlib-cpp",
         "//y2019/control_loops/drivetrain:drivetrain_base",