Fix TestAccApigeeInstance_apigeeInstanceServiceAttachmentBasicTestExample to use valid consumer_accept_list

[roaks3]

fixes hashicorp/terraform-provider-google#14777

This test was intentionally written with the 123456 value, which is obviously not a real resource. The test was passing for many months, so I suspect validation was added that caused this test to start failing.

If this PR is for Terraform, I acknowledge that I have:

• Searched through the issue tracker for an open issue that this either resolves or contributes to, commented on it to claim it, and written "fixes {url}" or "part of {url}" in this PR description. If there were no relevant open issues, I opened one and commented that I would like to work on it (not necessary for very small changes).
• Ensured that all new fields I added that can be set by a user appear in at least one example (for generated resources) or third_party test (for handwritten resources or update tests).
• Generated Terraform providers, and ran make test and make lint in the generated providers to ensure it passes unit and linter tests.
• Ran relevant acceptance tests using my own Google Cloud project and credentials (If the acceptance tests do not yet pass or you are unable to run them, please let your reviewer know).
• Read the Release Notes Guide before writing my release note below.

Release Note Template for Downstream PRs (will be copied)

[modular-magician]

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

Diff report

Your PR generated some diffs in downstreams - here they are.

Terraform GA: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
Terraform Beta: Diff ( 1 file changed, 1 insertion(+), 1 deletion(-))
TF Conversion: Diff ( 2 files changed, 3 insertions(+), 3 deletions(-))

[modular-magician]

Tests analytics

Total tests: 2758
Passed tests 2466
Skipped tests: 283
Affected tests: 9

Action taken

Found 9 affected test(s) by replaying old test recordings. Starting RECORDING based on the most recent commit. Click here to see the affected tests

TestAccBillingSubaccount_basic|TestAccBillingSubaccount_renameOnDestroy|TestAccDataSourceGoogleFirebaseAndroidAppConfig|TestAccComputeFirewallPolicyRule_multipleRules|TestAccApigeeKeystoresAliasesPkcs12_ApigeeKeystoresAliasesPkcs12Example|TestAccAlloydbBackup_missingLocation|TestAccApigeeKeystoresAliasesKeyCertFile_apigeeKeystoresAliasesKeyCertFileTestExample|TestAccAlloydbCluster_missingLocation|TestAccDataSourceAlloydbLocations_basic

Get to know how VCR tests work

[modular-magician]

Tests passed during RECORDING mode:
TestAccDataSourceGoogleFirebaseAndroidAppConfig[Debug log]
TestAccApigeeKeystoresAliasesPkcs12_ApigeeKeystoresAliasesPkcs12Example[Debug log]
TestAccAlloydbBackup_missingLocation[Debug log]
TestAccApigeeKeystoresAliasesKeyCertFile_apigeeKeystoresAliasesKeyCertFileTestExample[Debug log]
TestAccAlloydbCluster_missingLocation[Debug log]
TestAccDataSourceAlloydbLocations_basic[Debug log]

Tests failed during RECORDING mode:
TestAccBillingSubaccount_basic[Error message] [Debug log]
TestAccBillingSubaccount_renameOnDestroy[Error message] [Debug log]
TestAccComputeFirewallPolicyRule_multipleRules[Error message] [Debug log]

Please fix these to complete your PR
View the build log or the debug log for each test

[roaks3]

This is skipped in VCR, so ran it locally after the change:

=== RUN   TestAccApigeeInstance_apigeeInstanceServiceAttachmentBasicTestExample
=== PAUSE TestAccApigeeInstance_apigeeInstanceServiceAttachmentBasicTestExample
=== CONT  TestAccApigeeInstance_apigeeInstanceServiceAttachmentBasicTestExample
--- PASS: TestAccApigeeInstance_apigeeInstanceServiceAttachmentBasicTestExample (2710.97s)
PASS
ok  	github.com/hashicorp/terraform-provider-google/google	2711.648s

[hao-nan-li]

LGTM