fix(plugin-proposal-function-bind): fix invalid code emitted for ::super.foo

[uhyo]

Q	A
Fixed Issues?	none
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

This PR fixes the handling of super in plugin-proposal-function-bind.
Current implementation emits invalid code when converting ::super.foo.

example

Input

class C {
  foo() {
    ::super.bar;
    ::super.baz(123);
  }
}

Current Output

class C {
  foo() {
    super.bar.bind(super);
    super.baz.call(super, 123);
  }

}

New Output

class C {
  foo() {
    super.bar.bind(this);
    super.baz.call(this, 123);
  }

}

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/27773/

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[JLHwung]

Thanks!

[existentialism]

@uhyo thanks for the PR!