Fix test isolation: Add missing ensure.HelmHome(t) to TestExtractPluginInSubdirectory

This test was writing to the user's actual Helm data and cache directories

Signed-off-by: Scott Rigby <scott@r6by.com>

internal/plugin/installer/http_installer_test.go

@@ -515,6 +515,7 @@ func TestExtractWithExistingDirectory(t *testing.T) {
 }
 
 func TestExtractPluginInSubdirectory(t *testing.T) {
+	ensure.HelmHome(t)
 	source := "https://repo.localdomain/plugins/subdir-plugin-1.0.0.tar.gz"
 	tempDir := t.TempDir()