Bump upper bounds of build dependencies.

[jonathanknowles]

Related Issue: #61

This PR:

• bumps the following version bounds:

  - containers >= 0.5 && < 0.8
  + containers >= 0.5 && < 0.9
  
  - random     >= 1.1 && < 1.3
  + random     >= 1.1 && < 1.4

• adds GHC 9.12 to the list of supported compilers, for consistency with the CI build matrix:
  

  nothunks/.github/workflows/ci.yml

  Lines 15 to 16 in 11bb093

  	matrix:
  	ghc: ["8.10", "9.0", "9.2", "9.4", "9.6", "9.8", "9.10", "9.12"]

I was able to successfully build and test with the following command:

cabal test all \
    --constraint=containers==0.8 \
    --constraint=random==1.3.0 \
    --allow-newer=ghc-heap:containers \
    --allow-newer=wl-pprint-annotated:containers \
    --allow-newer=hashable:containers

[jonathanknowles]

Hi @coot
Hope this PR works for you. Let me know if you'd like any changes.

[coot]

LGTM