fix: Improve code coverage reporting in codecov (#2715)

* fix: Remove explicit coverpkg github.com/coder/coder/codersdk

This package is already covered by ./...

* fix: Ignore test utils in coverage (clitest, coderdtest, ptytest)

.github/codecov.yml

@@ -34,3 +34,7 @@ ignore:
   - scripts
   - site/.storybook
   - rules.go
+  # Packages used for writing tests.
+  - cli/clitest
+  - coderd/coderdtest
+  - pty/ptytest

.github/workflows/coder.yaml

@@ -297,7 +297,7 @@ jobs:
           # systems.
           if [ "${{ matrix.os }}" == "ubuntu-latest" ]; then
             echo ::set-output name=cover::true
-            export COVERAGE_FLAGS='-covermode=atomic -coverprofile="gotests.coverage" -coverpkg=./...,github.com/coder/coder/codersdk'
+            export COVERAGE_FLAGS='-covermode=atomic -coverprofile="gotests.coverage" -coverpkg=./...'
           else
             echo ::set-output name=cover::false
           fi