Interesting. Didn't remember that event & had to read up on it. That lead me to Wikipedia.
"The uprising came to an end officially when the Soviet Red Army entered Prague to liberate it."
Acc. to Wikipedia, the uprising ended with a ceasefire (officially German capitulation) on 8 May. The Germans "capitulated" because the agreement allowed them to escape to the West, so that they could surrender to the US-Americans.
So, when the Soviets arrived in Prague on 9 May there was not much left to liberate & only some scattered German units left to fight.