Tighten remaining shallow text assertions in subgraph preview output

text_for_success_includes_the_schema and text_for_failure_includes_the_errors
still used assert!(text.contains(...)) after the earlier pass only fixed
the two explicitly-flagged tests in this file. Switched to full-value
equality, matching the equivalent (already-tight) tests on the
contract side.

Author: sirdodger

src/command/subgraph/preview/output.rs

@@ -110,15 +110,29 @@ mod tests {
         let mut mock_response = response(AsyncBuildStatus::Success);
         mock_response.api_schema = Some("type Query { hello: String }".to_string());
         let text = SubgraphPreviewOutput(mock_response).text();
-        assert!(text.contains("type Query { hello: String }"));
+        assert_eq!(
+            text,
+            indoc! {"
+                Build id: build-123
+                Status: SUCCESS
+                Schema:
+
+                type Query { hello: String }"}
+        );
     }
 
     #[test]
     fn text_for_failure_includes_the_errors() {
         let mut mock_response = response(AsyncBuildStatus::ComposeFailed);
         mock_response.errors = vec!["[Accounts] -> Things went really wrong".to_string()];
         let text = SubgraphPreviewOutput(mock_response).text();
-        assert!(text.contains("[Accounts] -> Things went really wrong"));
+        assert_eq!(
+            text,
+            indoc! {"
+                Build id: build-123
+                Status: COMPOSE_FAILED
+                [Accounts] -> Things went really wrong"}
+        );
     }
 
     #[test]