Update Workerman to Ubuntu 20.04 (#5691)

frameworks/PHP/workerman/workerman-async.dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:19.10
+FROM ubuntu:20.04
 
 ARG DEBIAN_FRONTEND=noninteractive
 

frameworks/PHP/workerman/workerman-pgsql.dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:19.10
+FROM ubuntu:20.04
 
 ARG DEBIAN_FRONTEND=noninteractive
 

frameworks/PHP/workerman/workerman.dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:19.10
+FROM ubuntu:20.04
 
 ARG DEBIAN_FRONTEND=noninteractive