make: update to ubuntu:24.04 to fix readline issue

With older make, the newer make code results in this error:
../make/readline.mk:13: *** unterminated call to function 'eval': missing ')'.  Stop.

Newer versions of make work fine.

impls/make/Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:xenial
+FROM ubuntu:24.04
 MAINTAINER Joel Martin <github@martintribe.org>
 
 ##########################################################
@@ -9,7 +9,8 @@ MAINTAINER Joel Martin <github@martintribe.org>
 RUN apt-get -y update
 
 # Required for running tests
-RUN apt-get -y install make python
+RUN apt-get -y install make python3
+RUN ln -fs /usr/bin/python3 /usr/local/bin/python
 
 # Some typical implementation and test requirements
 RUN apt-get -y install curl libreadline-dev libedit-dev