cmd/go/internal/modload: remove go116EnableNarrowAll constant

This constant existed in case there was a serious problem with the
change to the "all" pattern in Go 1.16 (CL 240623), so that we could
roll back the change in behavior by just flipping the constant without
introducing merge conflicts elsewhere.

Go 1.16 has been out for a while and the new "all" behavior seems fine,
so we can jettison this feature flag.

For #36460

Change-Id: Ic2730edcee81514d56c7086e11542468eb63c84a
Reviewed-on: https://go-review.googlesource.com/c/go/+/303431
Trust: Bryan C. Mills <[email protected]>
Run-TryBot: Bryan C. Mills <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Jay Conrod <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>

Author: Bryan C. Mills

src/cmd/go/internal/modload/modfile.go

@@ -29,7 +29,6 @@ import (
 // module-module "all" pattern no longer closes over the dependencies of
 // tests outside of the main module.
 const narrowAllVersionV = "v1.16"
-const go116EnableNarrowAll = true
 
 var modFile *modfile.File
 
@@ -300,9 +299,6 @@ func indexModFile(data []byte, modFile *modfile.File, needsFix bool) *modFileInd
 // (Otherwise — as in Go 1.16+ — the "all" pattern includes only the packages
 // transitively *imported by* the packages and tests in the main module.)
 func (i *modFileIndex) allPatternClosesOverTests() bool {
-	if !go116EnableNarrowAll {
-		return true
-	}
 	if i != nil && semver.Compare(i.goVersionV, narrowAllVersionV) < 0 {
 		// The module explicitly predates the change in "all" for lazy loading, so
 		// continue to use the older interpretation. (If i == nil, we not in any