cue/parser: remove last vestiges of <foo>: T

This was once the notation for pattern constraints.

Signed-off-by: Marcel van Lohuizen <mpvl@gmail.com>
Change-Id: Iccf91c81a13f30a2a44c7e7cf16a5ef12784ee7a
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/547011
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cue/parser/parser.go

@@ -908,7 +908,6 @@ func (p *parser) parseField() (decl ast.Decl) {
 			p.errf(l.Pos(), "square bracket must have exactly one element")
 		}
 
-		tok := p.tok
 		label, expr, _, ok := p.parseLabel(true)
 		if !ok || (p.tok != token.COLON && p.tok != token.OPTION) {
 			if expr == nil {
@@ -921,7 +920,7 @@ func (p *parser) parseField() (decl ast.Decl) {
 		m.Value = &ast.StructLit{Elts: []ast.Decl{field}}
 		m = field
 
-		if tok != token.LSS && p.tok == token.OPTION {
+		if p.tok == token.OPTION {
 			m.Optional = p.pos
 			p.next()
 		}