projects: drop the two diagram refs that never had files

gpu-as-code and global-infra-modernisation pointed at diagrams that do not
exist, rendering a dead image box on a light card. Removing the key is
better than a broken frame until real art lands. Prompt pack for all six
covers ships alongside, in the blog-hero visual language.

src/content/projects/global-infra-modernisation.md

@@ -7,7 +7,6 @@ period: "2019 – 2025"
 stack: ["VMware / vSphere", "Azure (Blob, AVS)", "Microsoft 365", "SD-WAN", "Aruba ClearPass", "Palo Alto / FortiGate", "Veeam"]
 featured: false
 order: 40
-diagram: "globe"
 ---
 
 ## Problem

src/content/projects/gpu-as-code.md

@@ -7,7 +7,6 @@ period: "2025 – Present"
 stack: ["GPU passthrough", "ESXi", "DCGM Exporter", "Prometheus", "Bash", "Watchdogs"]
 featured: false
 order: 30
-diagram: "gpu"
 ---
 
 ## Problem