`onPush.default.enable` does not exist, but is documented

[SomeoneSerge]

hercules-ci-effects/flake-modules/herculesCI-attribute.nix

Line 172 in 0cc800c

It can be disabled by setting `onPush.default.enable = false;`.

Closes hercules-ci/flake-parts#125

[krad246]

Running into this too. However for now what I've done is force value of default. i.e.

onPush.default.outputs = lib.modules.mkForce {};