fi-0121: Deprecated attribute

Some official attributes are deprecated and should no longer be used. For example, the @layout attribute is deprecated:

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/bad/fi-0121.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}

In this case, @layout was replaced with @for_deperecated_c_bindings, so that attribute should be used instead:

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

{% includecode gerrit_repo="fuchsia/fuchsia" gerrit_path="tools/fidl/fidlc/tests/fidl/good/fi-0121.test.fidl" exclude_regexp="\/\/ (Copyright 20|Use of|found in).*" %}