fix: gemini flash -> pro for mcp smoke tests

[alexhancock]

Should be more reliable at the cost of a small amount of build time

[katzdave]

Still seems to be failing with pro; should we just drop/modify that specific test condition?

[alexhancock]

@katzdave The failure was actually unrelated to the model here. I think this should be more reliable. If it proves not to be once in main + everyone's PRs we can revisit.