This was forgotten when we worked around #2573

For namespace foo { namespace bar {} } we produce the following AST:
TSModuleDeclaration[id = foo] > TSModuleBlock > TSModuleDeclaration[id = bar] > TSModuleBlock

For namespace foo.bar {} produces the following AST:
TSModuleDeclaration[id = foo] > TSModuleDeclaration[id = bar] > TSModuleBlock

The AST we produce is driven by the AST TS produces - they emit the nested module declaration, so our code does as well.
Ultimately however is pretty incorrect and does not correctly represent the code as written.

Instead we should emit an EntityName, thus allowing TSQualifiedName in the .id:
TSModuleDeclaration[id = foo.bar] > TSModuleBlock