fix: remove unneeded dependencies

[shalvah]

Removes our dependency on @types/express, fixing #907. (Also removed @types/aws_lambda.( Inlined the types directly; we don't really need the in-depth type info, since we aren't the end user.

[subzero10]

I'm being completely honest here, please don't hate me :)

This feels like a solution that will come to bite us in the future.

• We are going down a path where we will have to manually mirror the work of the open-source community.
• We are losing any type-checking that we could have done with dependabot and our CI checks.
• We won't be able to trust that type checking will alert us from API changes, since we have to manually maintain them.

I also replied on Slack with more detailed thoughts.

[joshuap]

I'll defer to @subzero10 on this! @shalvah let's wait to discuss further until after Pan's back from parental leave. In the meantime I think that we can just tell users to add the type dependencies if they need them, right?