Fix MessagePack JS package peer dependency

The @aspnet/signalr-protocol-msgpack package has a peer dependency on @aspnet/signalr. This is good, but the value is static and hasn’t been updated since 1.0.0-preview3. We should either add automation to update the peer dependency on every build, or just remove it, or maybe make it a real dependency.

[BrennanConroy]

This is fixed in the preview7 build

[mikaelm12]

Acceptance checklist (check one item)

• We decided not to take this fix.
• The fix is tests-only.
• This is a Docs issue.
• The fix contains product changes (check all items below).
  • Relevant XML documentation comments for new public APIs are present. - Not needed
  • Narrative docs (docs.microsoft.com) are updated. (check one item below)
    • The change requires a new article. An issue with an outline has been filed here: [ISSUE LINK]
    • The change requires a change to an existing article. A closed docs PR with these changes is linked here: [PR LINK]
    • The change requires no docs changes.
  • Verification has been completed. (check one item below)
    • The change is in the shared framework and was verified against the following versions
      • SDK installer: [VERSION]
      • ASP.NET Core Runtime: [VERSION]
      • .NET Core Runtime: [VERSION]
    • The change is in an OOB NuGet/NPM/JAR package and was verified against the following version of that package: aspnet-signalr-protocol-msgpack-3.0.0-preview7.19325.7