Updated Nginx Proxy Manager to version 2.8.1.

Author: jlesage

Dockerfile

@@ -12,7 +12,7 @@ ARG DOCKER_IMAGE_VERSION=unknown
 
 # Define software versions.
 ARG OPENRESTY_VERSION=1.19.3.1
-ARG NGINX_PROXY_MANAGER_VERSION=2.8.0
+ARG NGINX_PROXY_MANAGER_VERSION=2.8.1
 ARG NGINX_HTTP_GEOIP2_MODULE_VERSION=3.3
 ARG LIBMAXMINDDB_VERSION=1.5.0
 ARG WATCH_VERSION=0.3.1
@@ -355,7 +355,6 @@ COPY rootfs/ /
 
 # Set environment variables.
 ENV APP_NAME="Nginx Proxy Manager" \
-    KEEP_APP_RUNNING=1 \
     DISABLE_IPV6=0
 
 # Define mountable directories.