OpenAI: explicit value for MaxToken and Temp

Because when k8sgpt talks with vLLM, the default MaxToken is 16,
which is so small.
Given the most model supports 2048 token(like Llama1 ..etc), so
put here for a safe value.

Signed-off-by: Peter Pan <Peter.Pan@daocloud.io>

pkg/ai/openai.go

@@ -66,6 +66,8 @@ func (c *OpenAIClient) GetCompletion(ctx context.Context, prompt string, promptT
 				Content: fmt.Sprintf(promptTmpl, c.language, prompt),
 			},
 		},
+		MaxTokens:   2048,
+		Temperature: 0.7,
 	})
 	if err != nil {
 		return "", err