Provide a separate variable for `OTLP_GOOGLE_CLOUD_PROJECT`

[sethvargo]

This was just an fyi, as a note for myself to probably provide a separate variable for OTLP_GOOGLE_CLOUD_PROJECT

Originally posted by @jerop in #212 (comment)

[gemini-cli]

🤖 Hi @sethvargo, I've received your request, and I'm working on it now! You can track my progress in the logs for more details.

[gemini-cli]

🤖 I'm sorry @sethvargo, but I was unable to process your request. Please see the logs for more details.

[jerop]

We already have an issue for this: #67