Exclude SpannedTestUtils from build

The SpannedTestUtils class which is built into the production
Dialer app contains references to JUnit. Rather then embed JUnit in
Dialer it was excluded from the build. It is not actually used at
all anywhere in Dialer app so may even be able to be deleted.

Bug: 30188076
Test: make checkbuild
Change-Id: I10c2c5f315e442477be81726e7df20d569fe5305
Merged-In: I37a618deba48d87a1a03d82ad4022233b408a788