bigtable: fix TestAccBigtableTable_familyType immutable-field ExpectError regex

[SirGitsalot]

Fixes nightly acceptance test failure for TestAccBigtableTable_familyType.

Root Cause & Fix

When the test attempts to change a column family's aggregate type (intmax -> intmin), the Bigtable API rejects the modification and returns an error indicating immutable fields. Previously, the error message only listed a single field:
Immutable fields 'value_type.aggregate_type' cannot be updated.

The API can now include additional immutable fields in the message (e.g., Immutable fields 'value_type.aggregate_type,sql_type' cannot be updated.).

This fix loosens the ExpectError regex in mmv1/third_party/terraform/services/bigtable/resource_bigtable_table_test.go to tolerate additional fields while continuing to verify that value_type.aggregate_type is reported as immutable.

[modular-magician]

Hi there, I'm the Modular magician. I've detected the following information about your changes for commit c3c0ce5:

Diff report

Your PR generated the following diffs in downstream repositories:

Repository	Diff Link	Changes
google provider	View Diff	1 file changed, 1 insertion(+), 1 deletion(-)
google-beta provider	View Diff	1 file changed, 1 insertion(+), 1 deletion(-)

Test report

Analytics

Total Tests	Passed	Skipped	Affected
67	0	67	0

Affected Service Packages

• bigtable

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[SirGitsalot]

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[github-actions]

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