Mark `template-haskell` non-upgradable (again)
65e9b88bc849e76040ed7947591ea7172cd02db5 made template-haskell non-upgradable
65ae95c191b19ec1884a4d80afbdaba9c3d477d1 made it upgradable again
...and this commit makes it non-upgradable again
While there may be a few cases when `template-haskell` can be
reinstalled, it's generally not advisable, and causes more harm than the
benefit in the few cases where we'd gain install-plan
flexibility (e.g. when only template-haskell's API is needed for
compile, but no actual TH evaluation takes place).
Closes #4098