In this task, you need to replace a letter in the sentence with another given letter.

Example Input: Sentence: 'a hipster riding a skateboard up the side of a wall'. Replace the letter 's' with 'm' in the sentence.
Example Output: a hipmter riding a mkateboard up the mide of a wall

Example Input: Sentence: 'a teddy bear dressed in denim is laying on a floor'. Replace the letter 'i' with 'd' in the sentence.
Example Output: a teddy bear dressed dn dendm ds laydng on a floor

Example Input: Sentence: 'two giraffes walk in a grassy area with shrubs'. Replace the letter 'a' with 'g' in the sentence.
Example Output:
two girgffes wglk in g grgssy greg with shrubs

