Move snyk to devDependencies

[madbence]

I don't think that snyk is a real dependency, so i moved it to devDependencies

[madbence]

@czardoz could you merge this, please? :smile_cat:

[cwalther]

Yes please – having it as a dependency, in addition to installing a lot of unneeded stuff, now causes warnings like this when installing on node 8, even though npm-cli-login itself still works fine on node 8:

npm WARN notsup Unsupported engine for [email protected]: wanted: {"node":">=10"} (current: {"node":"8.17.0","npm":"6.14.7"})
npm WARN notsup Not compatible with your version of node/npm: [email protected]

due to

+-- [email protected]
...
| `-- [email protected]
|   +-- @snyk/[email protected]
|   | +-- @snyk/[email protected] extraneous
|   | +-- @snyk/[email protected] deduped
|   | `-- [email protected]
|   +-- @snyk/[email protected]
|   | +-- @snyk/[email protected] deduped
|   | +-- @snyk/[email protected] deduped
|   | +-- [email protected]
|   | +-- [email protected] extraneous
...