mosquitto: bump to 2.0.15

Changelog: https://mosquitto.org/blog/2022/08/version-2-0-15-released/
Changelog: https://mosquitto.org/blog/2021/11/version-2-0-14-released/

2.0.15 is bigger security and bugfix release.  2.0.14 had a couple of
  minor changes and was skipped for OpenWrt.

Signed-off-by: Karl Palsson <karlp@etactica.com>

net/mosquitto/Makefile

@@ -9,7 +9,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mosquitto
-PKG_VERSION:=2.0.13
+PKG_VERSION:=2.0.15
 PKG_RELEASE:=1
 PKG_LICENSE:=EPL-2.0
 PKG_LICENSE_FILES:=LICENSE.txt
@@ -17,7 +17,7 @@ PKG_CPE_ID:=cpe:/a:eclipse:mosquitto
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://mosquitto.org/files/source/
-PKG_HASH:=9cf83a558f1588e8798edd8647b1632af88e88ef2cd45054e903c517df5bd2cd
+PKG_HASH:=4735b1d32e3f91c7a8896741d88a3022e89730a1ee897946decfa0df27039ac6
 
 include $(INCLUDE_DIR)/package.mk