[flake]: TestBatchedAssetIssuance/basic_asset_creation flake

[jtobin]

This test was observed failing flakily in a CI run for #1766 under the "unit tests (unit-race)" job:

--- FAIL: TestBatchedAssetIssuance (114.32s)
    --- FAIL: TestBatchedAssetIssuance/basic_asset_creation (68.32s)
        test_sqlite.go:11: Creating new SQLite DB handle for testing: /tmp/TestBatchedAssetIssuancebasic_asset_creation1941933153/001/tmp.db
        planter_test.go:1181:
            	Error Trace:	/home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:709
            	            				/home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:1181
            	            				/home/runner/work/taproot-assets/taproot-assets/tapgarden/planter_test.go:2099
            	Error:      	Received unexpected error:
            	            	predicate not satisfied after time out
            	Test:       	TestBatchedAssetIssuance/basic_asset_creation

The full log from that run can be viewed here.