fi-0178: Unused import {:#fi-0178}

Not referencing a dependency imported via the using declaration is an error:

{% include “docs/reference/fidl/language/error-catalog/label/_bad.md” %}

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0178.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}

Make sure all such imports are used in the library importing, either by actually referencing the import, or removing the unused dependency:

{% include “docs/reference/fidl/language/error-catalog/label/_good.md” %}

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0178.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}