fix(docker): match https prefix

lib/datasource/docker/index.js

@@ -19,7 +19,7 @@ function massageRegistry(input, registryUrls) {
   if (!registry || registry === 'docker.io') {
     registry = 'index.docker.io';
   }
-  if (!registry.match('$https?://')) {
+  if (!registry.match('^https?://')) {
     registry = `https://${registry}`;
   }
   return registry;

test/datasource/__snapshots__/docker.spec.js.snap

@@ -193,13 +193,13 @@ exports[`api/docker getPkgReleases uses custom registry 1`] = `
 [MockFunction] {
   "calls": Array [
     Array [
-      "https://https://registry.company.com/v2/",
+      "https://registry.company.com/v2/",
       Object {
         "throwHttpErrors": false,
       },
     ],
     Array [
-      "https://https://registry.company.com/v2/library/node/tags/list?n=10000",
+      "https://registry.company.com/v2/library/node/tags/list?n=10000",
       Object {
         "headers": Object {},
         "json": true,