Remove prototype schema

[kdawgwilk]

I think we were incorrectly using the prototype schema to define directives but if we move them directly to the schema we get these errors. This may be a bug in absinthe or a lack in our understanding of the purpose of the prototype schema

== Compilation error in file test/absinthe/federation/schema_test.exs ==
** (Absinthe.Schema.Error) Compilation failed:
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## Locations
/Users/kwilk/Sources/github/DivvyPayHQ/absinthe_federation/lib/absinthe/federation/schema/directive.ex:30

Unknown directive `extends'.
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## Locations
/Users/kwilk/Sources/github/DivvyPayHQ/absinthe_federation/lib/absinthe/federation/schema/directive.ex:30

Unknown directive `external'.
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## Locations
/Users/kwilk/Sources/github/DivvyPayHQ/absinthe_federation/lib/absinthe/federation/schema/directive.ex:30

Unknown directive `key'.


    (absinthe 1.7.0) lib/absinthe/schema.ex:366: Absinthe.Schema.__after_compile__/2
    (stdlib 3.17) lists.erl:1267: :lists.foldl/3
    test/absinthe/federation/schema_test.exs:4: (module)
    (elixir 1.13.2) lib/kernel/parallel_compiler.ex:455: Kernel.ParallelCompiler.require_file/2
    (elixir 1.13.2) lib/kernel/parallel_compiler.ex:348: anonymous fn/5 in Kernel.ParallelCompiler.spawn_workers/7

[kdawgwilk]

@benwilson512 Hopefully this helps explain what we are running into. We could use some clarity on if we are misusing the prototype schema