cmd/go: tweak wording of module path mismatch error message

Changes "was loaded as" to "was required as". This is slightly more
precise, since it hints at a requirement edge in the module version
graph.

Updates #28489

Change-Id: I636268c33f1ea9858c214fe275f271538186ed6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/186377
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/modload/load.go

@@ -1138,7 +1138,7 @@ func (r *mvsReqs) required(mod module.Version) ([]module.Version, error) {
 	if mpath := f.Module.Mod.Path; mpath != origPath && mpath != mod.Path {
 		return nil, module.VersionError(mod, fmt.Errorf(`parsing go.mod:
 	module declares its path as: %s
-	          but was loaded as: %s`, mod.Path, mpath))
+	        but was required as: %s`, mod.Path, mpath))
 	}
 	if f.Go != nil {
 		r.versions.LoadOrStore(mod, f.Go.Version)

src/cmd/go/testdata/script/mod_load_badchain.txt

@@ -59,27 +59,27 @@ func Test(t *testing.T) {}
 go get: example.com/badchain/c@v1.0.0 updating to
 	example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: example.com/badchain/c
-	          but was loaded as: example.com/badchain/wrong
+	        but was required as: example.com/badchain/wrong
 -- update-a-expected --
 go get: example.com/badchain/a@v1.1.0 requires
 	example.com/badchain/b@v1.1.0 requires
 	example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: example.com/badchain/c
-	          but was loaded as: example.com/badchain/wrong
+	        but was required as: example.com/badchain/wrong
 -- list-expected --
 go: example.com/badchain/a@v1.1.0 requires
 	example.com/badchain/b@v1.1.0 requires
 	example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: example.com/badchain/c
-	          but was loaded as: example.com/badchain/wrong
+	        but was required as: example.com/badchain/wrong
 -- list-missing-expected --
 go: m/use imports
 	example.com/badchain/c: example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: example.com/badchain/c
-	          but was loaded as: example.com/badchain/wrong
+	        but was required as: example.com/badchain/wrong
 -- list-missing-test-expected --
 go: m/testuse tested by
 	m/testuse.test imports
 	example.com/badchain/c: example.com/badchain/c@v1.1.0: parsing go.mod:
 	module declares its path as: example.com/badchain/c
-	          but was loaded as: example.com/badchain/wrong
+	        but was required as: example.com/badchain/wrong