DEV: (cmds) update INCREX command page for recent API change

[dwdougherty]

Redis 8.8 feature

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Note

Low Risk
Low risk: documentation and diagram updates only, but they reflect a behavioral/API change (default out-of-bounds handling and option names) that could confuse users if inaccurate.

Overview
Updates the INCREX command docs to match the new out-of-bounds API: removes OVERFLOW <FAIL|SAT|REJECT> in favor of a SATURATE flag, and documents that the default on bound/type-limit violations is now to skip the operation and return [current_value, 0].

Refreshes syntax strings, option descriptions, examples (including the rate-limiter snippet), return-value notes, and the railroad diagram (static/images/railroad/increx.svg) accordingly.

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[github-actions]

DOC-6643

[github-actions]

Staging links:
https://redis.io/docs/staging/DOC-6643/commands/increx
https://redis.io/docs/staging/DOC-6643/commands/increx/

[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}

[andy-stark-redis]

LGTM

[dwdougherty]

TYVM, @andy-stark-redis!