b997eee8_CCG___What_s_That_Inside_Joke___In_joke
[Card] Liz Shaw - Too Competent [Exp.] AW [Type] Ref PQ [In-joke] 
The subtitle refers to the producers' opinion of the Liz character as too much of an equal for the Doctor, remedied by this being her last story. Last story? That's the reason for the choice of quote.
Unauthorized Dr. Who CCG - What's That Inside Joke?
In-joke