Fix value of deprecated 'az.ai.openai' enum back to 'az.ai.openai'

[trentm]

I believe there was a small error in #1698. When 'az.ai.openai' was
deprecated, its 'value' should not have changed:
https://github.com/open-telemetry/semantic-conventions/pull/1698/files#diff-0936f2641601c5b370b10dfb33c8f82d6d731a2663cf042eef2aa5114c720902R71

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Aside, I noticed this when generating the changelog for the JS semconv package for v1.36.0. The generated changelog included:

8 exported values changed

...
GEN_AI_SYSTEM_VALUE_AZ_AI_OPENAI               // "az.ai.openai" -> "azure.ai.openai"

This stuck out as odd (the JS constant identifier doesn't match the new value).

[trentm]

I used bug_fix in the changelog entry. Not sure if deprecation would be preferred.

[trentm]

The yamllint check failure:

% make yamllint
yamllint .
./.chloggen/trentm-az.ai.openai-value-fix.yaml
  13:201    error    line too long (214 > 200 characters)  (line-length)

(FWIW running make chlog-validate passed. I understand running yamllint requires installing a Python dep, so cannot necessarily be run with make chlog-validate.)

I guess I cannot write long changelog entries? I guess I can try subtext.

[trentm]

The markdown-link-check failure:

[home/repo/docs/general/metrics.md]:
[TIMEOUT] https://unitsofmeasure.org/ucum.html | Timeout

That site doesn't load for me at all. I guess it is down.
We could add skip of that site to .lychee.toml I guess?

[trentm]

The markdown-link-check failure:

#2494 to fix this.

[trentm]

IIUC, this change is no longer necessary. This small change was handled as part of the bigger #2046 which made this correction while also deprecating gen_ai.system (in favour of gen_ai.provider.name). Specifically here:

https://github.com/open-telemetry/semantic-conventions/pull/2046/files#diff-86d5c795ed85e10660bee5cfaa78265f38ba124244a1179b764f6b738bafc458R91-R94