Apply suggestions from code review

- Fix Tekton versions
- Indicate release versions are expected, based on past history.

ROADMAP.md

@@ -13,13 +13,13 @@ availability and release stability.
 
 - v0.15: week of 2025-02-28
   - Kubernetes version: 1.32
-  - Tekton Pipelines version: 0.65
+  - Tekton Pipelines version: 0.68-LTS (expected)
 - v0.16: week of 2025-05-30
-  - Kubernetes version: 1.33
-  - Tekton Pipelines version: 0.68
+  - Kubernetes version: 1.33 (expected)
+  - Tekton Pipelines version: 0.71-LTS (expected)
 - v0.17: week of 2025-08-29
-  - Kubernetes version: 1.33
-  - Tekton Pipelines version: 0.71
+  - Kubernetes version: 1.33 or 1.34 (expected)
+  - Tekton Pipelines version: 0.74-LTS
 - v0.18: week of 2025-11-28
-  - Kubernetes version: 1.34
-  - Tekton Pipelines version: 0.74
+  - Kubernetes version: 1.34 (expected)
+  - Tekton Pipelines version: 0.77-LTS (expected)