Show band stretch in actuator assembly instructions

From #440 (closed) and !507 (merged).

• Add a step in the renders for the band insertion that shows the band being stretched to reach onto the actuator column prongs
• Consider the position of the cut-away in frames 2-5 It actually looks fine
• Consider the clash of the actuator tool and the actuator column prongs in frame 4
  
• Adjust the wording of the instructions to match the renders

Closes: #440 (closed)