backupccl: don't disable leases in test

[stevendanna]

399e56b introduced a bounded staleness read into the migration machinery.

When lease.TestingDisableTableLeases() has been set, this bounded staleness read encounters an error:

testcluster.go:384: migration-job-find-already-completed: cannot
set fixed timestamp, txn "sql txn" meta={id=f4142488 key=/Min
pri=0.01688073 epo=0 ts=1669334862.467371575,0
min=1669334862.467371575,0 seq=0} lock=false stat=PENDING
rts=1669334862.467371575,0 wto=false gul=1669334862.967371575,0
already performed reads

I believe that the read that was already performed in this case was the descriptor lookup. Then, when we go to execute the select, we attempt to SetFixedTimestamp in txn.NegotiateAndSend.

When the testing isn't in use, on its face it looks like we don't hit this case because we don't allow a fallback to a store lookup:

cockroach/pkg/sql/catalog/descs/leased_descriptors.go

Lines 143 to 159 in b5be006

	if err != nil {
	_, isBoundedStalenessRead := txn.(*maxTimestampBoundDeadlineHolder)
	// Read the descriptor from the store in the face of some specific errors
	// because of a known limitation of AcquireByName. See the known
	// limitations of AcquireByName for details.
	// Note we never should read from store during a bounded staleness read,
	// as it is safe to return the schema as non-existent.
	if shouldReadFromStore =
	!isBoundedStalenessRead && ((catalog.HasInactiveDescriptorError(err) &&
	errors.Is(err, catalog.ErrDescriptorDropped)) ||
	errors.Is(err, catalog.ErrDescriptorNotFound)); shouldReadFromStore {
	return nil, true, nil
	}
	// Lease acquisition failed with some other error. This we don't
	// know how to deal with, so propagate the error.
	return nil, false, err
	}

But, when TestingDisableTableLeases is set, we skip right to the store lookup:

cockroach/pkg/sql/catalog/descs/descriptor.go

Lines 489 to 491 in b5be006

	if flags.AvoidLeased || flags.RequireMutable || lease.TestingTableLeasesAreDisabled() {
	return continueLookups, descpb.InvalidID, nil
	}

I haven't looked into why lease.TestingDisableTableLeases() was in place in the past, but it is no longer used in any other backup tests and isn't likely needed here.

Fixes #92432
Fixes #92433
Fixes #92434
Fixes #92435

Release note: None

[cockroach-teamcity]

This change is 

[stevendanna]

bors r=adityamaru

[craig]

Build failed:

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[stevendanna]

Build failures were #92485 and #92493

[stevendanna]

bors retry

[craig]

Build failed:

• Bazel Essential CI (Cockroach)

[stevendanna]

bors retry

[craig]

Build failed (retrying...):

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[craig]

Build failed (retrying...):

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[craig]

Build succeeded:

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