LJSpeech alignment scripts fixed for latest MFA
The latest releases of MFA breaks extract_ljspeech_phonemes_and_durs.sh

Example:
```
~/NeMo/scripts/dataset_processing/ljspeech$ mfa thirdparty
usage: mfa [-h]
           {version,align,adapt,train,validate,g2p,train_g2p,model,train_lm,train_dictionary,train_ivector,classify_speakers,create_segments,transcribe,configure,history,annotator,anchor}
           ...
mfa: error: argument subcommand: invalid choice: 'thirdparty' (choose from 'version', 'align', 'adapt', 'train', 'validate', 'g2p', 'train_g2p', 'model', 'train_lm', 'train_dictionary', 'train_ivector', 'classify_speakers', 'create_segments', 'transcribe', 'configure', 'history', 'annotator', 'anchor')

~/NeMo/scripts/dataset_processing/ljspeech$ mfa download acoustic english
usage: mfa [-h]
           {version,align,adapt,train,validate,g2p,train_g2p,model,train_lm,train_dictionary,train_ivector,classify_speakers,create_segments,transcribe,configure,history,annotator,anchor}
           ...
mfa: error: argument subcommand: invalid choice: 'download' (choose from 'version', 'align', 'adapt', 'train', 'validate', 'g2p', 'train_g2p', 'model', 'train_lm', 'train_dictionary', 'train_ivector', 'classify_speakers', 'create_segments', 'transcribe', 'configure', 'history', 'annotator', 'anchor')
``` 

Latest version uses conda-forge and also changed "mfa download" to "mfa model download".
Described in 
https://github.com/MontrealCorpusTools/Montreal-Forced-Aligner/issues/349#issuecomment-966610658

This is related to TTS (@blisc?)