Bump Ubuntu versions in README and bug report template

Author: peace-maker

.github/ISSUE_TEMPLATE/bug_report.md

@@ -39,7 +39,7 @@ You should see `[DEBUG]` statements that show what's happening behind the scenes
 
 ## Verify on Ubuntu
 
-If possible, please verify that your issue occurs on 64-bit Ubuntu 18.04.  We provide a Dockerfile based on Ubuntu 18.04 via `docker.io` to make this super simple, no VM required!
+If possible, please verify that your issue occurs on 64-bit Ubuntu 22.04.  We provide a Dockerfile based on Ubuntu 22.04 via `docker.io` to make this super simple, no VM required!
 
 ```sh
 # Download the Docker image

README.md

@@ -32,7 +32,7 @@ To get you started, we've provided some example solutions for past CTF challenge
 
 # Installation
 
-Pwntools is best supported on 64-bit Ubuntu LTS releases (14.04, 16.04, 18.04, and 20.04).  Most functionality should work on any Posix-like distribution (Debian, Arch, FreeBSD, OSX, etc.).  
+Pwntools is best supported on 64-bit Ubuntu LTS releases (18.04, 20.04, 22.04, and 24.04).  Most functionality should work on any Posix-like distribution (Debian, Arch, FreeBSD, OSX, etc.).  
 
 Python3 is suggested, but Pwntools still works with Python 2.7.  Most of the functionality of pwntools is self-contained and Python-only.  You should be able to get running quickly with