refactor(github): Remove unused `etag` support for PR cache (#17665)

lib/modules/platform/github/api-cache.spec.ts

@@ -205,23 +205,4 @@ describe('modules/platform/github/api-cache', () => {
       expect(needNextPage).toBeFalse();
     });
   });
-
-  describe('etag', () => {
-    it('returns null', () => {
-      const apiCache = new ApiCache({ items: {} });
-      expect(apiCache.etag).toBeNull();
-    });
-
-    it('sets and retrieves non-null value', () => {
-      const apiCache = new ApiCache({ items: {} });
-      apiCache.etag = 'foobar';
-      expect(apiCache.etag).toBe('foobar');
-    });
-
-    it('deletes value for null parameter', () => {
-      const apiCache = new ApiCache({ items: {} });
-      apiCache.etag = null;
-      expect(apiCache.etag).toBeNull();
-    });
-  });
 });

lib/modules/platform/github/api-cache.ts

@@ -5,18 +5,6 @@ import type { ApiPageCache, ApiPageItem } from './types';
 export class ApiCache<T extends ApiPageItem> {
   constructor(private cache: ApiPageCache<T>) {}
 
-  get etag(): string | null {
-    return this.cache.etag ?? null;
-  }
-
-  set etag(value: string | null) {
-    if (value === null) {
-      delete this.cache.etag;
-    } else {
-      this.cache.etag = value;
-    }
-  }
-
   /**
    * @returns Date formatted to use in HTTP headers
    */

lib/modules/platform/github/types.ts

@@ -145,5 +145,4 @@ export interface ApiPageItem {
 export interface ApiPageCache<T extends ApiPageItem = ApiPageItem> {
   items: Record<number, T>;
   lastModified?: string;
-  etag?: string;
 }