update roundcube to php 7.4

webmails/roundcube/Dockerfile

@@ -1,10 +1,10 @@
 # NOTE: only add file if building for arm
 ARG ARCH=""
 ARG QEMU=other
-FROM ${ARCH}php:7.3-apache as build_arm
+FROM ${ARCH}php:7.4-apache as build_arm
 ONBUILD COPY --from=balenalib/rpi-alpine:3.10 /usr/bin/qemu-arm-static /usr/bin/qemu-arm-static
 
-FROM ${ARCH}php:7.3-apache as build_other
+FROM ${ARCH}php:7.4-apache as build_other
 
 FROM build_${QEMU}
 #Shared layer between rainloop and roundcube