Go: fix highlighting of non-reserved keywords (atoms)

[madelinekalil]

codemirror5/mode/go/go.js

Line 30 in 78555dd

var atoms = {

Words in this list are highlighted as special keywords regardless of context. For example, it is valid in Go to create a variable called "new". It should only receive special highlighting when used as the builtin function new(expr), and should be treated as a variable otherwise.