Remove unused proctest dependency

[alexfmpe]

Fixes CI which started failing recently since text 2.1.2 broke proctest build and thus a test suite here.
proctest is not actually used here, only declared so easy fix.
haskell/text#608
https://github.com/alexfmpe/reflex/actions/runs/11654426219/job/32447941922#step:5:948

Error:     Ambiguous occurrence ‘show’
    It could refer to
       either ‘Prelude.show’,
Error: cabal: Failed to build proctest-0.1.3.0. See the build log above for
details.

              imported from ‘Prelude’ at Test/Proctest.hs:65:8-20
              (and originally defined in ‘GHC.Show’)
           or ‘Data.Text.show’,
              imported from ‘Data.Text’ at Test/Proctest.hs:104:1-16
    |
196 |     msg = "Test.Proctest.Timeout: " ++ show n ++ " microseconds do not fit into Int"
    |                                        ^^^^
Error: Process completed with exit code 1.