chore: update releases.toml for forc-client-0.71.3 and fix Slack notify CI

[JoshuaBatty]

Summary

• Append releases.toml entry for forc-client 0.71.3 (sway 0.71.2, fuel-core-types 0.48.0, fuels-rs 0.77.0) — missed because the release workflow job failed after a successful publish
• Upgrade ravsamhq/notify-slack-action from v1 to v2 across CI jobs; v1 runs on Python 3.7 and crashes importing functools.cache, which incorrectly failed the publish-crates job even though forc-client 0.71.3 published successfully

Test plan

• CI green
• Future release publish jobs complete without false failures on the Slack notify step

[cursor]

PR Summary

Low Risk
Release metadata and CI notification action pins only; no application or auth logic changes.

Overview
Records forc-client 0.71.3 in releases.toml (sway 0.71.2, fuel-core-types 0.48.0, fuels-rs 0.77.0) after the release workflow failed to update the file post-publish.

Bumps ravsamhq/notify-slack-action from v1 to v2 on the lint, test, and publish failure-notification steps in CI so Slack notify no longer breaks on deprecated Python 3.7 (functools.cache), which was marking publish jobs failed despite successful crate uploads.

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