php7: update to 7.4.15

This fixes:
    - CVE-2021-21702

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

lang/php7/Makefile

@@ -6,7 +6,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=php
-PKG_VERSION:=7.4.14
+PKG_VERSION:=7.4.15
 PKG_RELEASE:=1
 
 PKG_MAINTAINER:=Michael Heimpold <mhei@heimpold.de>
@@ -16,7 +16,7 @@ PKG_CPE_ID:=cpe:/a:php:php
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.xz
 PKG_SOURCE_URL:=http://www.php.net/distributions/
-PKG_HASH:=f9f3c37969fcd9006c1dbb1dd76ab53f28c698a1646fa2dde8547c3f45e02886
+PKG_HASH:=9b859c65f0cf7b3eff9d4a28cfab719fb3d36a1db3c20d874a79b5ec44d43cb8
 
 PKG_BUILD_PARALLEL:=1
 PKG_USE_MIPS16:=0