Drop signatures for public key fields where not needed.

[SanjayVas]

This is a breaking API change, but attempts to maintain wire-compatibility for EDP Requisition fulfillment.

[wfa-reviewable]

This change is 

[SanjayVas]

This is a follow-up to #185.

[stevenwarejones]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @SanjayVas)

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src/main/proto/wfa/measurement/api/v2alpha/measurement.proto line 78 at r1 (raw file):

      // (--
      // TODO(world-federation-of-advertisers/cross-media-measurement-api#188):
      // Remove this once the certificate is always specified in

you can remove this if you wait for PR 171 to merge first. wdyt?

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src/main/proto/wfa/measurement/api/v2alpha/requisition.proto line 84 at r1 (raw file):

  // Remove this once the certificate is always specified in
  // `FulfillDirectRequisitionRequest`. --)
  string data_provider_certificate = 6 [

ditto

[SanjayVas]

Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @stevenwarejones)

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src/main/proto/wfa/measurement/api/v2alpha/measurement.proto line 78 at r1 (raw file):

Previously, stevenwarejones (Steven Ware Jones) wrote…

you can remove this if you wait for PR 171 to merge first. wdyt?

Not quite. The always part here is important, meaning all EDPs need to be specifying the new field.

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src/main/proto/wfa/measurement/api/v2alpha/requisition.proto line 84 at r1 (raw file):

Previously, stevenwarejones (Steven Ware Jones) wrote…

ditto

Ditto.

[stevenwarejones]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @SanjayVas)

[SanjayVas]

Reviewed 1 of 2 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @stevenwarejones)