[Github Actions] Pin poetry to 1.8.5 to avoid speakeasy run failure.

[amenasria]

The Generate MISTRALAI workflow has been failing with:

  » Compile SDK...
                  
  Step: Compile SDK started
  INFO    Running command: poetry version 1.3.1	{"path":"/github/workspace/repo"}
  INFO    Running command: poetry lock --no-update	{"path":"/github/workspace/repo"}
  WARN    failed running commands: 
  
  Creating virtualenv mistralai in /github/workspace/repo/.venv
  
  The option "--no-update" does not exist

This issue was fixed in speakasy v1.467.0 but we're locked at speakeasy v1.462.2 because it was appending _ to attributes changing to much our SDK.

The error is coming from poetry that deprecated the --no-update flag, hence pinning poetry to 1.8.5 should solve the issue.