[web] Stop bolding AI features on the interstitial plans page (#34125)

* [web] Stop bolding AI features unconditionally on the interstitial

The four `strong: true` flags on the AI features in `sectionMain2026`
caused those rows to render bold on every interstitial visit, regardless
of paywall context. The original intent (per Design QA #34022) was for
boldness to highlight the features relevant to the specific paywall the
user came from (e.g. AI paywall -> AI features bolded) — that
conditional logic was never wired up, and currently no `purchaseReferrer`
or paywall reason is plumbed through to the feature config.

Remove the unconditional `strong: true` so the cards render consistently
with the pricing page. Reintroduce conditional bolding in a follow-up
once the paywall→features mapping is scoped by design.

Closes #34022

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Remove `card-include-strong` and related code

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
GitOrigin-RevId: 2112214217f3b53d34518efbca546082ce559e26

services/web/frontend/stylesheets/pages/plans-2026.scss

@@ -357,10 +357,6 @@
       padding-left: 0;
     }
 
-    .card-include-strong {
-      font-weight: 700;
-    }
-
     .card-includes-list-item.only-show-for-specific-plan-period {
       display: none;
     }