[DocsUI, Search]: Remove flaky time measure.

Removes time measure from the test. Garbage collection,
device type, and other factors can impact how much time passes
between documents provider releasing next set results and those results
being delivered to the loader. The main thing is that these results are
delivered in 3 passes.

Bug: 436723718
Flag: com.android.documentsui.flags.use_search_v2_read_only
Test: atest DocumentsUIGoogleTests
Change-Id: I58119fc0521c9a7b1440bc09ff02491299fb6903