{kokoro} Add Catalog bridging header to bazel. (#6508)
{kokoro} Add Catalog bridging header to bazel. (#6508)

The catalog bridging header for Swift wasn't being included in bazel targets
and wasn't required to build the catalog. Adding it now so that all targets
have coverage and the bazel-coverage job can be made required.

Part of #6197
material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios,material-components/material-components-ios