Update requirements.txt and fix issue when rendering video with subtitles

Update requirements.txt and fix issue when rendering video with subtitles In moviepy version 1.0.3, CompositeVideoClip is a module within moviepy.video.compositing. To use it correctly, we need to import the CompositeVideoClip class from the module. This commit makes the following changes: - Update the import statement for CompositeVideoClip in videoclipper.py to import the class from the module. - Fix the moviepy version to 1.0.3 in requirements.txt to avoid unexpected behavior due to version upgrades. These changes resolve the issue encountered when rendering videos with subtitles using moviepy 1.0.3.