pigeonhole: reflect license of LGPL-2.1-or-later

Signed-off-by: W. Michael Petullo <mike@flyn.org>

mail/pigeonhole/Makefile

@@ -18,7 +18,7 @@ DOVECOT_VERSION:=2.3
 PKG_SOURCE:=dovecot-$(DOVECOT_VERSION)-pigeonhole-$(PKG_VERSION_PLUGIN).tar.gz
 PKG_SOURCE_URL:=https://pigeonhole.dovecot.org/releases/$(DOVECOT_VERSION)
 PKG_HASH:=8fb860d50c1b1a09aea9e25f8ee89c22e34ecedfb0e11a1c48a7f67310759022
-PKG_LICENSE:=LGPL-2.1
+PKG_LICENSE:=LGPL-2.1-or-later
 PKG_LICENSE_FILES:=COPYING COPYING.LGPL
 PKG_CPE_ID:=cpe:/a:dovecot:pigeonhole