fix error message for service metadata import

[masayoshi634]

I fix error message.

[heleeen]

Please fix test case 🙏

terraform-provider-mackerel/mackerel/resource_mackerel_service_metadata_test.go

Line 54 in 1396089

ExpectError: regexp.MustCompile("the ID must be in the form '<service name>:<namespace>'"),

[coveralls]

Pull Request Test Coverage Report for Build 1014360470

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.884%

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Totals
Change from base Build 977657354:	0.0%
Covered Lines:	2301
Relevant Lines:	2375

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💛 - Coveralls