chore: Bump gpb from 4.19.7 to 4.21.1

Bumps [gpb](https://github.com/tomas-abrahamsson/gpb) from 4.19.7 to 4.21.1.
- [Release notes](https://github.com/tomas-abrahamsson/gpb/releases)
- [Changelog](https://github.com/tomas-abrahamsson/gpb/blob/master/ChangeLog)
- [Commits](tomas-abrahamsson/gpb@4.19.7...4.21.1)

---
updated-dependencies:
- dependency-name: gpb
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Diff for: mix.lock

@@ -37,7 +37,7 @@
   "finch": {:hex, :finch, "0.14.0", "619bfdee18fc135190bf590356c4bf5d5f71f916adb12aec94caa3fa9267a4bc", [:mix], [{:castore, "~> 0.1", [hex: :castore, repo: "hexpm", optional: false]}, {:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.3", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.4", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 0.2.6", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "5459acaf18c4fdb47a8c22fb3baff5d8173106217c8e56c5ba0b93e66501a8dd"},
   "gettext": {:hex, :gettext, "0.22.0", "a25d71ec21b1848957d9207b81fd61cb25161688d282d58bdafef74c2270bdc4", [:mix], [{:expo, "~> 0.3.0", [hex: :expo, repo: "hexpm", optional: false]}], "hexpm", "cb0675141576f73720c8e49b4f0fd3f2c69f0cd8c218202724d4aebab8c70ace"},
   "goth": {:hex, :goth, "1.3.1", "f3e08a7f23ea8992ab92d2e1d5c72ea1a8fbd2fe3a46ad1b08d0620f71374fdc", [:mix], [{:finch, "~> 0.9", [hex: :finch, repo: "hexpm", optional: false]}, {:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}, {:jose, "~> 1.10", [hex: :jose, repo: "hexpm", optional: false]}], "hexpm", "90326c2c0a7acda7fb75fc4a4f0cba84945d8fcb22694d36c9967cec8949937c"},
-  "gpb": {:hex, :gpb, "4.19.7", "a0da133db34a62796cbffba8ae8210cc266a0e6303a79c5d92ceadc9bccc9cd0", [:make, :rebar3], [], "hexpm", "82d6a10474551b2c6d057082e05e2d7dfcfc1d22362f4bd5e9077456268d0578"},
+  "gpb": {:hex, :gpb, "4.21.1", "72e229c242d252d690addcfd04a6416c26c4d4d2c3521e05570a7a78b48d3bd1", [:make, :rebar3], [], "hexpm", "c05c9aea9e25bd341367a43b3d3eb68e951563911072259c5ec4cb6642f4ef22"},
   "hackney": {:hex, :hackney, "1.18.1", "f48bf88f521f2a229fc7bae88cf4f85adc9cd9bcf23b5dc8eb6a1788c662c4f6", [:rebar3], [{:certifi, "~> 2.9.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~> 6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~> 1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~> 1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.3.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~> 1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~> 0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "a4ecdaff44297e9b5894ae499e9a070ea1888c84afdd1fd9b7b2bc384950128e"},
   "hpax": {:hex, :hpax, "0.1.2", "09a75600d9d8bbd064cdd741f21fc06fc1f4cf3d0fcc335e5aa19be1a7235c84", [:mix], [], "hexpm", "2c87843d5a23f5f16748ebe77969880e29809580efdaccd615cd3bed628a8c13"},
   "httpoison": {:hex, :httpoison, "2.0.0", "d38b091f5e481e45cc700aba8121ce49b66d348122a097c9fbc2dc6876d88090", [:mix], [{:hackney, "~> 1.17", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "f1253bf455be73a4c3f6ae3407e7e3cf6fc91934093e056d737a0566126e2930"},