[about page] move CTA sponsors box into a sub component

frontend/src/app/components/about/about-sponsors.component.ts

@@ -0,0 +1,9 @@
+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'app-about-sponsors',
+  templateUrl: './about-sponsors.component.html',
+  styleUrls: ['./about-sponsors.component.scss'],
+})
+export class AboutSponsorsComponent {
+}