Remove Babylon plugins for features already merged to the ECMAScript spec (#8448)

These are now enabled by default:
- objectRestSpread (2018)
- asyncGenerators (2018)
- optionalCatchBInding (2019)
- jsonStrings (2019)

TODO (after this commit):
- [ ] Deprecate the `@babel/plugin-syntax-*` packages.
- [ ] Deprecate the `@babel/plugin-proposal-*` packages.
- [ ] Create the `@babel/plugin-transform-*` packages.

packages/babel-core/src/transformation/util/missing-plugin-helper.js

@@ -1,16 +1,6 @@
 // @flow
 
 const pluginNameMap = {
-  asyncGenerators: {
-    syntax: {
-      name: "@babel/plugin-syntax-async-generators",
-      url: "https://git.io/vb4SY",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-async-generator-functions",
-      url: "https://git.io/vb4yp",
-    },
-  },
   classProperties: {
     syntax: {
       name: "@babel/plugin-syntax-class-properties",
@@ -143,26 +133,6 @@ const pluginNameMap = {
       url: "https://git.io/vb4yS",
     },
   },
-  objectRestSpread: {
-    syntax: {
-      name: "@babel/plugin-syntax-object-rest-spread",
-      url: "https://git.io/vb4y5",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-object-rest-spread",
-      url: "https://git.io/vb4Ss",
-    },
-  },
-  optionalCatchBinding: {
-    syntax: {
-      name: "@babel/plugin-syntax-optional-catch-binding",
-      url: "https://git.io/vb4Sn",
-    },
-    transform: {
-      name: "@babel/plugin-proposal-optional-catch-binding",
-      url: "https://git.io/vb4SI",
-    },
-  },
   optionalChaining: {
     syntax: {
       name: "@babel/plugin-syntax-optional-chaining",
@@ -203,6 +173,41 @@ const pluginNameMap = {
       url: "https://git.io/vb4Sm",
     },
   },
+
+  // TODO: This plugins are now supported by default by @babel/parser: they can
+  // be removed from this list. Although removing them isn't a breaking change,
+  // it's better to keep a nice error message for users using older versions of
+  // the parser. They can be removed in Babel 8.
+  asyncGenerators: {
+    syntax: {
+      name: "@babel/plugin-syntax-async-generators",
+      url: "https://git.io/vb4SY",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-async-generator-functions",
+      url: "https://git.io/vb4yp",
+    },
+  },
+  objectRestSpread: {
+    syntax: {
+      name: "@babel/plugin-syntax-object-rest-spread",
+      url: "https://git.io/vb4y5",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-object-rest-spread",
+      url: "https://git.io/vb4Ss",
+    },
+  },
+  optionalCatchBinding: {
+    syntax: {
+      name: "@babel/plugin-syntax-optional-catch-binding",
+      url: "https://git.io/vb4Sn",
+    },
+    transform: {
+      name: "@babel/plugin-proposal-optional-catch-binding",
+      url: "https://git.io/vb4SI",
+    },
+  },
 };
 
 const getNameURLCombination = ({ name, url }) => `${name} (${url})`;