chore(test): Remove unit testing log output for success cases (#293)

During running the unit tests we see output like

=== RUN   TestIssueService_DeleteAttachment
    TestIssueService_DeleteAttachment: issue_test.go:587: Attachment deleted
    TestIssueService_DeleteAttachment: issue_test.go:592: No error

This log can be removed, because this mostly confirms the success case.
The opposite case is throwing a testing error, which is visible as well.
Hence, there is no need to log this messages durcing testing

issue_test.go

@@ -583,13 +583,10 @@ func TestIssueService_DeleteAttachment(t *testing.T) {
 		if resp.StatusCode == 404 {
 			t.Error("Attachment not found")
 		}
-	} else {
-		t.Log("Attachment deleted")
 	}
+
 	if err != nil {
 		t.Errorf("Error given: %s", err)
-	} else {
-		t.Log("No error")
 	}
 }