Remove unused visitor portal helpers

Brand and public file serving replaced the old org/portal
logo and report URL generators, leaving dead methods and
unused Service fields behind.

Signed-off-by: Bryan Frimin <bryan@probo.com>

pkg/complianceportal/visitor/errors.go

@@ -30,7 +30,6 @@ var (
 	ErrUserNotFound           = errors.New("user not found")
 	ErrUserInactive           = errors.New("user inactive")
 	ErrDocumentAccessNotFound = errors.New("document access not found")
-	ErrNDAFileNotFound        = errors.New("NDA file not found")
 	ErrDocumentNotFound       = errors.New("document not found")
 	ErrDocumentNotVisible     = errors.New("document not visible")
 	ErrReportNotFound         = errors.New("report not found")