fix(manager): regex manager digest (#5783)

lib/manager/regex/__snapshots__/index.spec.ts.snap

 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`manager/custom/extract extracts multiple dependencies 1`] = `
+exports[`manager/regex/index extracts multiple dependencies 1`] = `
 Object {
   "deps": Array [
     Object {

lib/manager/regex/index.spec.ts

 import { readFileSync } from 'fs';
 import { resolve } from 'path';
-import { extractPackageFile } from '.';
+import { extractPackageFile, defaultConfig } from '.';
+import { getName } from '../../../test/util';
 
 const dockerfileContent = readFileSync(
   resolve(__dirname, `./__fixtures__/Dockerfile`),
   'utf8'
 );
-describe('manager/custom/extract', () => {
+describe(getName(__filename), () => {
+  it('has default config', () => {
+    expect(defaultConfig).toEqual({
+      pinDigests: false,
+    });
+  });
   it('extracts multiple dependencies', async () => {
     const config = {
       matchStrings: [

lib/manager/regex/index.ts

@@ -5,7 +5,9 @@ import { logger } from '../../logger';
 
 export const autoReplace = true;
 
-export const defaultConfig = {};
+export const defaultConfig = {
+  pinDigests: false,
+};
 
 export function extractPackageFile(
   content: string,