test(workflows): avoid pinning serde error locations

Assert the stable unknown-operation meaning instead of serde line and column text.

Co-authored-by: Other Brother Darryl <cee32d92756729ee0c097c5661b879c6199931cd25315c8cf398dcbf0f155cf1@buzz.block.builderlab.xyz>

Signed-off-by: Logan Johnson <loganj@squareup.com>

crates/buzz-core/src/workflow_owner_command.rs

@@ -529,12 +529,11 @@ mod tests {
             .tags(event.tags)
             .sign_with_keys(&owner)
             .unwrap();
-        assert_eq!(
-            parse_owner_command(&event),
-            Err(WorkflowOwnerError::InvalidContent(
-                "unknown variant `update`, expected one of `start`, `pause`, `resume`, `cancel`, `restore`".into()
-            ))
-        );
+        let error = parse_owner_command(&event).unwrap_err();
+        assert!(matches!(error, WorkflowOwnerError::InvalidContent(message)
+            if message.contains("unknown variant `update`")
+                && message.contains("expected one of")
+                && message.contains("`restore`")));
 
         let event = command(&owner, &agent, WorkflowOwnerOperation::Start);
         let event = EventBuilder::new(