gopls/internal/regtest: skip failing test for go1.13 and below

I missed that this test was failing when fixing the 1.12 build, because
I forgot that I moved the regtests to the gopls module. Hoisted by my
own petard.

Change-Id: I1cf601e730fa7bb92885f55b68845b539e57e1a0
Reviewed-on: https://go-review.googlesource.com/c/tools/+/253937
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
diff --git a/gopls/internal/regtest/completion_test.go b/gopls/internal/regtest/completion_test.go
index 957a829..b21ff44 100644
--- a/gopls/internal/regtest/completion_test.go
+++ b/gopls/internal/regtest/completion_test.go
@@ -12,9 +12,11 @@
 	"golang.org/x/tools/internal/lsp"
 	"golang.org/x/tools/internal/lsp/fake"
 	"golang.org/x/tools/internal/lsp/protocol"
+	"golang.org/x/tools/internal/testenv"
 )
 
 func TestPackageCompletion(t *testing.T) {
+	testenv.NeedsGo1Point(t, 14)
 	const files = `
 -- go.mod --
 module mod.com