Temporarily disable avbHashtreeNotUsingSha1 due to false negatives

This test fails due to other tests disabling Android Verified Boot
during CTS runs.  This causes many false negatives.  A fix is being
tracked in b/267521823.

Temporarily disable the test while the fix is implemented.

Test: Run `atest VerifiedBootTest#avbHashtreeNotUsingSha1`.
Change-Id: I1c168a0d3ac9097d6b1eeddc39f6feea475fd4cd
1 file changed