[chore]: Update async-tcp submodule to latest bugfix commit.

- Point async-tcp submodule to f8eba155, which restores correct ownership transfer in ephemeral_bridging_function and fixes a use-after-free caused by a previous bad merge.
- All other changes are minor doc and formatting updates.

Signed-off-by: Goran Mišković <[email protected]>

Author: schkovich