Remove links to plugins that are part of the library now

Author: marijnh

acorn/README.md

@@ -260,9 +260,7 @@ The utility spits out the syntax tree as JSON data.
 Plugins for ECMAScript proposals:
 
  - [`acorn-stage3`](https://github.com/acornjs/acorn-stage3): Parse most stage 3 proposals, bundling:
-   - [`acorn-bigint`](https://github.com/acornjs/acorn-bigint): Parse [BigInt proposal](https://github.com/tc39/proposal-bigint)
    - [`acorn-class-fields`](https://github.com/acornjs/acorn-class-fields): Parse [class fields proposal](https://github.com/tc39/proposal-class-fields)
-   - [`acorn-dynamic-import`](https://github.com/kesne/acorn-dynamic-import): Parse [import() proposal](https://github.com/tc39/proposal-dynamic-import)
    - [`acorn-import-meta`](https://github.com/acornjs/acorn-import-meta): Parse [import.meta proposal](https://github.com/tc39/proposal-import-meta)
    - [`acorn-numeric-separator`](https://github.com/acornjs/acorn-numeric-separator): Parse [numeric separator proposal](https://github.com/tc39/proposal-numeric-separator)
    - [`acorn-private-methods`](https://github.com/acornjs/acorn-private-methods): parse [private methods, getters and setters proposal](https://github.com/tc39/proposal-private-methods)n