(MODULES-11832) Drop redundant platform matrix result section

Remove the standalone `## Platform matrix result` section from the synced
PR template. GitHub already renders the PR's CI status checks at the bottom
of every PR, so a section asking contributors to manually paste a CI link
was redundant busywork (per review feedback on #643).

The one genuinely-useful case -- the supported-OS acceptance matrix that
runs nightly via Litmus rather than on the PR itself -- is folded into the
existing checklist item instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: imaqsood

moduleroot/.github/PULL_REQUEST_TEMPLATE.md.erb

@@ -20,13 +20,9 @@ flag any unrelated cleanup as a separate ticket/PR.
 
 - [ ] Linked the driving `MODULES-*` ticket above using the structured spec template.
 - [ ] Coverage gate is green (or the baseline is preserved -- coverage was not reduced).
-- [ ] Platform matrix result link included below (CI run or nightly Litmus result).
+- [ ] Platform matrix is green -- the PR's CI checks below cover it, or link a recent nightly Litmus run if the supported-OS acceptance tests do not run on this PR.
 - [ ] `Co-Authored-By: Claude` trailer is present on the commits if this PR was AI-assisted.
 
-## Platform matrix result
-
-<!-- Paste the link to the CI / nightly Litmus run that proves the supported OS matrix is green. -->
-
 ## Review policy (outcome-based)
 
 PRs are judged on outcomes, not line counts. Pick the lane that matches this change so