docs: explain how to set bridge network driver options

[lsh1215]

Supersedes #7075.

What changed

Addresses @dvdksn's review feedback on #7075 for the Bridge driver options section of docker network create:

• Reworded the section intro to explain that driver options are set with the --opt flag (kept the existing note about the equivalent docker0/daemon flags, since the table's second column relies on that context).
• Removed the redundant enable_ip_masquerade paragraph, so the example now sits directly below the table as a general illustration of how to set a bridge driver option.

Why

Follow-up to docker/docs#13861 and the review discussion on #7075. The existing table already lists com.docker.network.bridge.enable_ip_masquerade, but the section didn't show how driver options are actually passed on the command line.

Validation

• make mddocs / make yamldocs — regenerated cleanly, no changes outside the reworked prose
• git diff --check

This is a documentation-only change; it does not change Docker CLI or daemon behavior.

[lsh1215]

@thaJeztah only the DCO check has run on this one — the other workflows that ran on #7075 don't seem to have been triggered here. Does the workflow run need maintainer approval? Happy to know if a milestone needs setting too.

This supersedes #7075 and applies dvdksn's review from there.