Test fix: TestImportFilterLogging improve assertions

[bbrks]

https://mobile.jenkins.couchbase.com/job/sgw-unix-build/30160/

failed because there was also a Rosmar error logged, which caused the numErrors+1 assertion to fail.

2023-11-29T04:14:02.426-08:00 [ERR] c:#067 db:db Javascript: Import <ud>Error</ud> -- db.newImportFilterRunner.func1() at import.go:453
2023-11-29T04:14:02.426-08:00 [ERR] Rosmar: Bucket B#2 error expiring docs: this Rosmar bucket has been closed -- rosmar.logError() at logging.go:56
--- FAIL: TestImportFilterLogging (0.21s)
    import_test.go:583: 
        	Error Trace:	/home/couchbase/jenkins/workspace/sgw-unix-build/3.2.0/enterprise/sync_gateway/rest/importtest/import_test.go:583
        	Error:      	Not equal: 
        	            	expected: 3
        	            	actual  : 4
        	Test:       	TestImportFilterLogging

Tweak test to check for specific error message, and allow >= 1 error

Integration Tests

• n/a

[torcolvin]

I am OK to merge this but this test actually was the first sign, albeit not a good one, that there was a problem with the code in couchbaselabs/rosmar#17 . It is a timing issue, which is why it only showed up in jenkins.