fix(circleci): ignore machine images

Closes #8656

lib/manager/circleci/__snapshots__/extract.spec.ts.snap

@@ -13,16 +13,6 @@ Array [
     "replaceString": "cimg/node:14.8.0",
     "versioning": "docker",
   },
-  Object {
-    "autoReplaceStringTemplate": "{{depName}}{{#if newValue}}:{{newValue}}{{/if}}{{#if newDigest}}@{{newDigest}}{{/if}}",
-    "currentDigest": undefined,
-    "currentValue": "201903-01",
-    "datasource": "docker",
-    "depName": "ubuntu-1604",
-    "depType": "docker",
-    "replaceString": "ubuntu-1604:201903-01",
-    "versioning": "docker",
-  },
 ]
 `;
 

lib/manager/circleci/extract.ts

@@ -53,7 +53,12 @@ export function extractPackageFile(content: string): PackageFile | null {
         );
         dep.depType = 'docker';
         dep.versioning = 'docker';
-        deps.push(dep);
+        if (
+          !dep.depName?.startsWith('ubuntu-') &&
+          !dep.depName?.startsWith('windows-server-')
+        ) {
+          deps.push(dep);
+        }
       }
     }
   } catch (err) /* istanbul ignore next */ {