[FloatingActionButton] Fix labelOpacity property

[pubiqq]

This PR:

• Fixes an incorrect implementation of the Property#get(Object) method of the labelOpacity property:

  Before:

  @Override
  public Float get(ExtendedFloatingActionButton object) {
      int originalOpacity = Color.alpha(<original text color>);
      float currentOpacity = Color.alpha(<current text color>) / 255F;  // <-
      return lerp(0F, 1F, currentOpacity / originalOpacity);
  }

  After:

  @Override
  public Float get(ExtendedFloatingActionButton object) {
      int originalOpacity = Color.alpha(<original text color>);
      float currentOpacity = Color.alpha(<current text color>);  // <-
      return lerp(0F, 1F, currentOpacity / originalOpacity);
  }

• Simplifies the calculation of the target color in the Property#set(Object, Object) method. In particular, it eliminates unnecessary blah-blah / 255F * 255, which only result in a loss of accuracy.

• Avoids calculating the target color when it's not needed.

[kendrickumstattd]

Hey, there! Thanks for the PR. Could you provide some more context on how this fixes labelOpacity, including screenshots? Thanks.

[kendrickumstattd]

Happy to review this! Thanks for sending in the change. Could you include a description of how this fixes labelOpacity, including screenshots? Cheers!

[pubiqq]

Sure, I've added a description.