build(deps): update capnpc requirement from 0.14.2 to 0.16.4 in /gst-depth-meta-rs

Updates the requirements on capnpc to permit the latest version.

Commits

• 3b19644 prepare for capnpc-v0.16.4 release
• 620d6d6 remove PWD from environment, to silence warning from kj/filesystem-disk-unix
• 91b8682 better error handling in capnpc
• fd6fa0a add GeneratorContext.scope_map to avoid need to pass around parent_node_id
• e65b888 remove unneeded .iter()
• 14ebf02 get_qualified_module()
• 10f263e make populate_scope_map() a method of GeneratorContext
• e0bdf73 Manually implement Copy/Clone for generated readers.
• 06bdf01 remove unneeded reborrow()
• 66ed31b leading colons on capnp::Word
• Additional commits viewable in compare view