ci: Remove tracing and coverage

Coverage is quite low, and tracing slows down the tests. Coverage should
be handled again, but only for a single runner and not in the matrix
itself.

.github/workflows/elixir.yml

@@ -67,4 +67,4 @@ jobs:
       - name: Compile PropCheck
         run: mix compile --warnings-as-errors
       - name: Run Tests
-        run: PROPCHECK_NUMTESTS=200 PROPCHECK_SEARCH_STEPS=1000 mix tests --cover --trace
+        run: PROPCHECK_NUMTESTS=200 PROPCHECK_SEARCH_STEPS=1000 mix tests

mix.exs

@@ -13,7 +13,6 @@ defmodule PropCheck.Mixfile do
       elixirc_paths: elixirc_paths(Mix.env()),
       build_embedded: Mix.env() == :prod,
       start_permanent: Mix.env() == :prod,
-      test_coverage: [threshold: 0.58],
       package: package(),
       name: "PropCheck",
       homepage_url: @source_url,