cue/build: remove context.Context field

Despite remarks about cancellation, the context.Context
field isn't used. While we might add cancellation in the future,
that's easily done later, and for now this is somewhat misleading,
so remove the field and adjust the comment in question.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I5aa1380705bac1215b48a22d177f74639ea811e7
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/552266
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUEcueckoo <cueckoo@cuelang.org>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cue/build/context.go

@@ -26,15 +26,11 @@
 package build
 
 import (
-	"context"
-
 	"cuelang.org/go/cue/ast"
 )
 
 // A Context keeps track of state of building instances and caches work.
 type Context struct {
-	ctxt context.Context
-
 	loader    LoadFunc
 	parseFunc func(str string, src interface{}) (*ast.File, error)
 
@@ -80,14 +76,13 @@ func (inst *Instance) Complete() error {
 func (c *Context) init() {
 	if !c.initialized {
 		c.initialized = true
-		c.ctxt = context.Background()
 		c.imports = map[string]*Instance{}
 	}
 }
 
 // Options:
 // - certain parse modes
-// - parallellism
+// - parallelism
 // - error handler (allows cancelling the context)
 // - file set.
 

cue/load/config.go

@@ -124,9 +124,6 @@ type Config struct {
 	// packages at loading time.
 
 	// Context specifies the context for the load operation.
-	// If the context is cancelled, the loader may stop early
-	// and return an ErrCancelled error.
-	// If Context is nil, the load cannot be cancelled.
 	Context *build.Context
 
 	// A Module is a collection of packages and instances that are within the