[CI] Fix docs check (#2811)

# Motivation

I broke the docs check in one of my previous PRs.

# Modification

This PR fixes the docs check again.

# Result

No more broken CI

.github/workflows/soundness.yml

@@ -73,7 +73,7 @@ jobs:
       uses: actions/checkout@v4
     - name: Run documentation check
       run: |
-        apt-get -qq update && apt-get -qq -y install curl
+        apt-get -qq update && apt-get -qq -y install curl yq
         curl -s https://raw.githubusercontent.com/apple/swift-nio/main/scripts/check-docs.sh | bash
 
   unacceptable-language-check:

scripts/check-docs.sh

@@ -19,10 +19,9 @@ log() { printf -- "** %s\n" "$*" >&2; }
 error() { printf -- "** ERROR: %s\n" "$*" >&2; }
 fatal() { error "$@"; exit 1; }
 
-raw_targets=$(sed -E -n -e 's/^.* - documentation_targets: \[(.*)\].*$/\1/p' .spi.yml)
-targets=("${raw_targets//,/ }")
-
-for target in "${targets[@]}"; do
+log "Checking documentation targets..."
+for target in $(yq -r '.builder.configs[].documentation_targets[]' .spi.yml); do
+  log "Checking target $target..."
   swift package plugin generate-documentation --target "$target" --warnings-as-errors --analyze --level detailed
 done