internal/licenses: accept the HPND license

Approved by legal.

Change-Id: I80f47422ef885cbaaf395edc533e146ad41f0d04
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/279482
Trust: Jamal Carvalho <jamal@golang.org>
Run-TryBot: Jamal Carvalho <jamal@golang.org>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
diff --git a/internal/licenses/licenses.go b/internal/licenses/licenses.go
index 3090fb1..0738aca 100644
--- a/internal/licenses/licenses.go
+++ b/internal/licenses/licenses.go
@@ -148,6 +148,7 @@
 		"EUPL-1.2":             true,
 		"GPL2":                 true,
 		"GPL3":                 true,
+		"HPND":                 true,
 		"ISC":                  true,
 		"JSON":                 true,
 		"LGPL-2.1":             true,