Fix errcheck issue in subpath_test.go (#28791)

* Fix errcheck issue in subpath_test.go

* Fix govet error

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/.golangci.yml

@@ -259,7 +259,6 @@ issues:
         channels/testlib/helper.go|\
         channels/utils/fileutils/fileutils_test.go|\
         channels/utils/license_test.go|\
-        channels/utils/subpath_test.go|\
         channels/web/oauth.go|\
         channels/web/oauth_test.go|\
         channels/web/response_writer_wrapper_test.go|\