Fix cURL example to use $max_delay variable instead of hardcoded value

[Copilot]

Addresses review feedback on #6574 regarding inconsistent use of the max_delay parameter in the exponential backoff cURL example.

Changes

• Updated cURL example in content/shared/influxdb3-write-guides/troubleshoot-distributed.md to use $max_delay variable instead of hardcoded 30
• Passes max_delay as awk variable -v m=$max_delay and uses it in the comparison: if(d>m) d=m
• Makes cURL example consistent with Python and JavaScript examples which already use their respective max_delay variables

Before:

delay=$(awk -v b=$base -v a=$attempt 'BEGIN{d=b*(2^a); if(d>30) d=30; print d}')

After:

delay=$(awk -v b=$base -v a=$attempt -v m=$max_delay 'BEGIN{d=b*(2^a); if(d>m) d=m; print d}')

• Signed the InfluxData CLA
  (if necessary)
• Rebased/mergeable

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.