Remove unused babel/parser

[pjonsson]

What this PR does

The installation instructions
for Babel only list babel/core,
babel/cli, and babel/preset-env:

https://babeljs.io/docs/usage#overview

so remove babel/parser from
package.json.

The babel/parser is still used,
but babel/core controls
the version through its dependencies.

Test me

Run yarn gulp build, so tested by CI.

Checklist

• There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
• I've updated relevant documentation in doc/.
• I've updated CHANGES.md with what I changed.
• I've provided instructions in the PR description on how to test this PR.