fi-0088: Service members cannot be optional {:#fi-0088}

This error occurs when you mark a service member as optional. Marking a service member as optional isn't allowed because service members are always optional.

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0088.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}

To fix this, remove the optional clause:

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0088.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}