DO NOT MERGE Removed unused priority argument

Bug: 187080582

Make S consistent with T by removing the unused 'priority' argument from
findPreferredActivityNotLocked().  This is a subset of the changes made
under bug 194319951.

The sole purpose of this change is to allow further changes for this
bug can be committed into S and merge cleanly into T.

Test: atest
 * FrameworksServicesTests:PackageManagerServiceTest
Change-Id: I006eddb00b0ec06fda7364f0ac10446aff35fcb2