Definition: In this task, you need to remove all words of a given length in the sentence. The number of letters in a word determine its length, for example, the length of the word "apple" is 5.
Input: Sentence: 'a young boy sitting on a blue toy tractor with sheep next to him and the shadows of people casting down on the ground next to him'. Remove all words of length '6' in the given sentence.

a young boy sitting on a blue toy tractor with sheep next to him and the shadows of casting down on the next to him