test: fix datastore integration tests

[atierian]

Description

A few DataStore integration tests were consistently failing after moving away from AsyncExpectation / await wait(for:) to XCTestExpectation / await fulfillment(of:) in #3305

These failures were caused by double waits on a single expectation.

• Removes double wait in two remaining cases.

Another test was somewhat consistently failing due to a timeout. The test takes almost 10 seconds to run on my M1 Pro, so there's little chance it's going to make it before timing out in our CI.

• Increases timeout from 10 to 60 seconds.

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[atierian]

I ran the integration tests on this branch before opening the PR, so they're not visible from the PR itself.
Here they are:

• https://github.com/aws-amplify/amplify-swift/actions/runs/6591682034
• https://github.com/aws-amplify/amplify-swift/actions/runs/6591687018

[codecov-commenter]

Codecov Report

Merging #3317 (2d57a0e) into main (bdc9b4a) will decrease coverage by 0.20%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main    #3317      +/-   ##
==========================================
- Coverage   64.49%   64.30%   -0.20%     
==========================================
  Files        1075     1075              
  Lines       35891    35891              
==========================================
- Hits        23148    23078      -70     
- Misses      12743    12813      +70     

Flag	Coverage Δ
API_plugin_unit_test	67.07% <ø> (ø)
AWSPluginsCore	66.15% <ø> (ø)
Amplify	47.81% <ø> (-0.02%)	⬇️
Analytics_plugin_unit_test	81.37% <ø> (ø)
Auth_plugin_unit_test	74.09% <ø> (-0.01%)	⬇️
CoreMLPredictions_plugin_unit_test	59.44% <ø> (ø)
DataStore_plugin_unit_test	80.02% <ø> (-1.05%)	⬇️
Geo_plugin_unit_test	70.75% <ø> (ø)
Logging_plugin_unit_test	63.09% <ø> (ø)
Predictions_plugin_unit_test	37.29% <ø> (ø)
PushNotifications_plugin_unit_test	60.29% <ø> (ø)
Storage_plugin_unit_test	54.18% <ø> (ø)
unit_tests	64.30% <ø> (-0.20%)	⬇️

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see 10 files with indirect coverage changes

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