[AI] More robust thoughtTokenCount gemini 3 test (#15730)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: paulb777

FirebaseAI/Tests/TestApp/Tests/Integration/GenerateContentIntegrationTests.swift

@@ -85,7 +85,8 @@ struct GenerateContentIntegrationTests {
     #expect(promptTokensDetails.modality == .text)
     #expect(promptTokensDetails.tokenCount == usageMetadata.promptTokenCount)
     if modelName.hasPrefix("gemini-3") {
-      #expect(usageMetadata.thoughtsTokenCount == 64)
+      // For gemini-3 models, the thoughtsTokenCount can vary slightly between runs.
+      #expect(usageMetadata.thoughtsTokenCount >= 64)
     } else {
       #expect(usageMetadata.thoughtsTokenCount == 0)
     }