fix(cog.toml): Reactive the `nix flake check` step

Nix can now build Trinitrix again.

cog.toml

@@ -22,7 +22,7 @@ branch_whitelist = ["master"]
 ignore_merge_commits = false
 
 pre_bump_hooks = [
-  # "nix flake check",                     # verify the project builds
+  "nix flake check",                     # verify the project builds
   "./scripts/renew_copyright_header.sh", # update the license header in each file
   "cargo set-version {{version}}",       # bump version in Cargo.toml
   "nix fmt",                             # format