Don't recommend t2.micro for AWS

[yuvipanda]

Our docs recommend t2.micro on AWS, but I don't think it has enough memory. We should revise that.

I received the following signal when running TLJH on a t2.micro. Although the guide says it's possible, I don't think there is adequate memory on the instance. I think increasing the memory would solve the problem linked above "...install-failed-on-ec2"

[  118.818268] cloud-init[1126]: Downloading & setting up user environment...
[  151.623187] Out of memory: Killed process 7900 (python) total-vm:972292kB, anon-rss:703924kB, file-rss:0kB, shmem-rss:0kB, UID:0 pgtables:1536kB oom_score_adj:0

[  151.012740] cloud-init[1126]: Traceback (most recent call last):
[  151.028865] cloud-init[1126]:   File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
[  151.051882] cloud-init[1126]:     return _run_code(code, main_globals, None,
[  151.064108] cloud-init[1126]:   File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
[  151.094475] cloud-init[1126]:     exec(code, run_globals)
[  151.103613] cloud-init[1126]:   File "/opt/tljh/hub/lib/python3.8/site-packages/tljh/installer.py", line 534, in <module>
[  151.122858] cloud-init[1126]:     main()
[  151.137657] cloud-init[1126]:   File "/opt/tljh/hub/lib/python3.8/site-packages/tljh/installer.py", line 506, in main 
[  151.154607] cloud-init[1126]:     ensure_user_environment(args.user_requirements_txt_url)
[  151.168459] cloud-init[1126]:   File "/opt/tljh/hub/lib/python3.8/site-packages/tljh/installer.py", line 280, in ensure_user_environment
[  151.201095] cloud-init[1126]:     conda.ensure_conda_packages(USER_ENV_PREFIX, [
[  151.225931] cloud-init[1126]:   File "/opt/tljh/hub/lib/python3.8/site-packages/tljh/conda.py", line 103, in ensure_conda_packages
[  151.247188] cloud-init[1126]:     raw_output = subprocess.check_output(conda_executable + [
[  151.264364] cloud-init[1126]:   File "/usr/lib/python3.8/subprocess.py", line 411, in check_output
[  151.273829] cloud-init[1126]:     return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
[  151.283640] cloud-init[1126]:   File "/usr/lib/python3.8/subprocess.py", line 512, in run
[  151.292590] cloud-init[1126]:     raise CalledProcessError(retcode, process.args,
[  151.303086] cloud-init[1126]: subprocess.CalledProcessError: Command '['/opt/tljh/user/bin/python', '-m', 'conda', 'install', '-c', 'conda-forge', '--json', '--prefix', '/opt/tljh/user', 'conda==4.8.1']' died with <Signals.SIGKILL: 9>.

Originally posted by @jdelamare in #286 (comment)