Fix pynini install in TTS tutorials
Signed-off-by: Jocelyn Huang <jocelynh@nvidia.com>

# What does this PR do ?

Update TTS tutorials to install pynini with the new script.

**Collection**: TTS

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

# Additional Information
* Related to #4674 
