[chore][internal/testutil] run make modernize (#14158)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

Run the `make modernize` tool.

https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize

This is part of the process to enable the
[modernize](#14153)
linter in CI.

There are no changes in the component behaviour.

Signed-off-by: Paulo Dias <[email protected]>

Author: paulojmdias

internal/testutil/testutil.go

@@ -113,8 +113,8 @@ func createExclusionsList(tb testing.TB, exclusionsText string) []portpair {
 	require.Len(tb, parts, 3)
 	portsText := strings.Split(parts[2], "*")
 	require.Greater(tb, len(portsText), 1) // original text may have a suffix like " - Administered port exclusions."
-	lines := strings.Split(portsText[0], "\n")
-	for _, line := range lines {
+	lines := strings.SplitSeq(portsText[0], "\n")
+	for line := range lines {
 		if strings.TrimSpace(line) != "" {
 			entries := strings.Fields(strings.TrimSpace(line))
 			require.Len(tb, entries, 2)