makefile: remove underscore from openssh package version before inserting into image tag

Makefile

@@ -2,7 +2,7 @@
 
 DOCKER_IMAGE_NAME := docker.io/fphammerle/rsync-ssh
 DOCKER_TAG_VERSION := $(shell git describe --match=v* --abbrev=0 --dirty | sed -e 's/^v//')
-OPENSSH_SERVER_PACKAGE_VERSION := $(shell grep -Po 'OPENSSH_SERVER_PACKAGE_VERSION=\K.+' Dockerfile | tr -d -)
+OPENSSH_SERVER_PACKAGE_VERSION := $(shell grep -Po 'OPENSSH_SERVER_PACKAGE_VERSION=\K.+' Dockerfile | tr -d _-)
 RSYNC_PACKAGE_VERSION := $(shell grep -Po 'RSYNC_PACKAGE_VERSION=\K.+' Dockerfile | tr -d -)
 ARCH := $(shell arch)
 DOCKER_TAG_ARCH_SUFFIX_aarch64 := arm64