internal/licenses: accept the BSD-3-Clause-Clear license

Approved by legal.

Change-Id: I962a9848843aa2220cc9690be9e154d1eff04950
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/278954
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jamal Carvalho <jamal@golang.org>
diff --git a/internal/licenses/licenses.go b/internal/licenses/licenses.go
index 611188e..3090fb1 100644
--- a/internal/licenses/licenses.go
+++ b/internal/licenses/licenses.go
@@ -136,6 +136,7 @@
 		"BSD-2-Clause":         true,
 		"BSD-2-Clause-FreeBSD": true,
 		"BSD-3-Clause":         true,
+		"BSD-3-Clause-Clear":   true,
 		"BSL-1.0":              true,
 		"CC-BY-3.0":            true,
 		"CC-BY-4.0":            true,