Fix an invalid link in get_data.py of ljspeech
# What does this PR do ?

It fixes an invalid link in get_data.py of ljspeech. Usage of the link in line 63 leads to downloading a html file not a tsv file, so we need to change it to a raw link.

**Collection**: [TTS]

**PR Type**:
- [ ] New Feature
- [x] Bugfix
- [ ] Documentation