Run `dcm check-unused-code` over `devtools_test` (#9935)

.github/workflows/build.yaml

diff --git a/.github/workflows/build.yaml b/.github/workflows/build.yaml
index 8d969d4..b65550a 100644
--- a/.github/workflows/build.yaml
+++ b/.github/workflows/build.yaml
@@ -84,9 +84,8 @@
         run: |
           dcm analyze packages/devtools_app packages/devtools_app_shared packages/devtools_extensions packages/devtools_shared packages/devtools_test
       - name: Run dcm checks on packages
-        # TODO(https://github.com/flutter/devtools/issues/9906): run on all DevTools packages.
         run: |
-          dcm check-unused-code packages/devtools_app packages/devtools_app_shared packages/devtools_extensions packages/devtools_shared --exclude-public-api
+          dcm check-unused-code packages/devtools_app packages/devtools_app_shared packages/devtools_extensions packages/devtools_shared packages/devtools_test --exclude-public-api
 
   test-packages:
     name: ${{ matrix.os }} ${{ matrix.package }} test

analysis_options.yaml

diff --git a/analysis_options.yaml b/analysis_options.yaml
index 6d5d565..c98b130 100644
--- a/analysis_options.yaml
+++ b/analysis_options.yaml
@@ -170,10 +170,8 @@
     - packages/devtools_app/test/test_infra/test_data/**
   exclude:
     unused-code:
-      # TODO(https://github.com/flutter/devtools/issues/9906) remove these
-      # excludes as findings are resolved.
       # This fixture has unused code for testing the debugger.
-      - packages/devtools_app/test/test_infra/fixtures/**
+      - packages/devtools_app/test/test_infra/fixtures/flutter_app/**
       # Ignore unused code in package examples.
       - packages/devtools_app_shared/example/**
   rules: