content: update marketing team roles (#1962)

- **teams.marketing: Webmaster -> Web Lead**
- **teams.marketing: update Sigmanificient to Brand and Design
Developer**

Author: djacu

core/src/content/teams/080_marketing.mdx

@@ -7,13 +7,13 @@ members:
     title: Lead & Brand and Design Steward & Surveys and Metrics Coordinator
   - name: Thilo Billerbeck
     discourse: avocadoom
-    title: Webmaster
+    title: Web Lead
   - name: Florian Pester
     discourse: flyfloh
     title: Social Media Liaison
   - name: Yohann Boniface
     discourse: Sigmanificient
-    title: Brand and Design Steward
+    title: Brand and Design Developer
 contact:
   - name: Discourse
     href: https://discourse.nixos.org/c/dev/marketing-team/28