gopls: fix diagnostics integration test

CL 649355 improved simplifyrange suggested fix, thus the corresponding
diagnostics integration test must be updated, too.

Change-Id: Ief33cc4e9ab3d760c1af28c94102638f6d2b69e8
Reviewed-on: https://go-review.googlesource.com/c/tools/+/650556
Reviewed-by: Michael Knyszek <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Cuong Manh Le <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: cuonglm

gopls/internal/test/integration/diagnostics/diagnostics_test.go

@@ -562,7 +562,7 @@ func _() {
 		env.OpenFile("main.go")
 		var d protocol.PublishDiagnosticsParams
 		env.AfterChange(
-			Diagnostics(AtPosition("main.go", 5, 8)),
+			Diagnostics(AtPosition("main.go", 5, 6)),
 			ReadDiagnostics("main.go", &d),
 		)
 		if fixes := env.GetQuickFixes("main.go", d.Diagnostics); len(fixes) != 0 {