Bump postgrex from 0.15.7 to 0.15.8 (#712)

Bumps [postgrex](https://github.com/elixir-ecto/postgrex) from 0.15.7 to 0.15.8.
- [Release notes](https://github.com/elixir-ecto/postgrex/releases)
- [Changelog](https://github.com/elixir-ecto/postgrex/blob/master/CHANGELOG.md)
- [Commits](elixir-ecto/postgrex@v0.15.7...v0.15.8)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

mix.lock

@@ -65,7 +65,7 @@
   "plug": {:hex, :plug, "1.11.0", "f17217525597628298998bc3baed9f8ea1fa3f1160aa9871aee6df47a6e4d38e", [:mix], [{:mime, "~> 1.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.1.1 or ~> 1.2", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "2d9c633f0499f9dc5c2fd069161af4e2e7756890b81adcbb2ceaa074e8308876"},
   "plug_cowboy": {:hex, :plug_cowboy, "2.4.1", "779ba386c0915027f22e14a48919a9545714f849505fa15af2631a0d298abf0f", [:mix], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:cowboy_telemetry, "~> 0.3", [hex: :cowboy_telemetry, repo: "hexpm", optional: false]}, {:plug, "~> 1.7", [hex: :plug, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "d72113b6dff7b37a7d9b2a5b68892808e3a9a752f2bf7e503240945385b70507"},
   "plug_crypto": {:hex, :plug_crypto, "1.2.0", "1cb20793aa63a6c619dd18bb33d7a3aa94818e5fd39ad357051a67f26dfa2df6", [:mix], [], "hexpm", "a48b538ae8bf381ffac344520755f3007cc10bd8e90b240af98ea29b69683fc2"},
-  "postgrex": {:hex, :postgrex, "0.15.7", "724410acd48abac529d0faa6c2a379fb8ae2088e31247687b16cacc0e0883372", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm", "88310c010ff047cecd73d5ceca1d99205e4b1ab1b9abfdab7e00f5c9d20ef8f9"},
+  "postgrex": {:hex, :postgrex, "0.15.8", "f5e782bbe5e8fa178d5e3cd1999c857dc48eda95f0a4d7f7bd92a50e84a0d491", [:mix], [{:connection, "~> 1.0", [hex: :connection, repo: "hexpm", optional: false]}, {:db_connection, "~> 2.1", [hex: :db_connection, repo: "hexpm", optional: false]}, {:decimal, "~> 1.5 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}], "hexpm", "698fbfacea34c4cf22c8281abeb5cf68d99628d541874f085520ab3b53d356fe"},
   "quantum": {:hex, :quantum, "3.3.0", "e8f6b9479728774288c5f426b11a6e3e8f619f3c226163a7e18bccfe543b714d", [:mix], [{:crontab, "~> 1.1", [hex: :crontab, repo: "hexpm", optional: false]}, {:gen_stage, "~> 0.14 or ~> 1.0", [hex: :gen_stage, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "3b83ef137ab3887e783b013418b5ce3e847d66b71c4ef0f233b0321c84b72f67"},
   "que": {:hex, :que, "0.10.1", "788ed0ec92ed69bdf9cfb29bf41a94ca6355b8d44959bd0669cf706e557ac891", [:mix], [{:ex_utils, "~> 0.1.6", [hex: :ex_utils, repo: "hexpm", optional: false]}, {:memento, "~> 0.3.0", [hex: :memento, repo: "hexpm", optional: false]}], "hexpm", "a737b365253e75dbd24b2d51acc1d851049e87baae08cd0c94e2bc5cd65088d5"},
   "ranch": {:hex, :ranch, "1.7.1", "6b1fab51b49196860b733a49c07604465a47bdb78aa10c1c16a3d199f7f8c881", [:rebar3], [], "hexpm", "451d8527787df716d99dc36162fca05934915db0b6141bbdac2ea8d3c7afc7d7"},