update TTS readme (NVIDIA#7088)

* update TTS readme

Signed-off-by: Xuesong Yang <[email protected]>

---------

Signed-off-by: Xuesong Yang <[email protected]>
Signed-off-by: dorotat <[email protected]>

README.rst

@@ -115,11 +115,12 @@ Key Features
     * `Prompt Learning <https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/nlp/nemo_megatron/prompt_learning.html>`_
     * `NGC collection of pre-trained NLP models. <https://ngc.nvidia.com/catalog/collections/nvidia:nemo_nlp>`_
     * `Synthetic Tabular Data Generation <https://developer.nvidia.com/blog/generating-synthetic-data-with-transformers-a-solution-for-enterprise-data-challenges/>`_
-* `Speech synthesis (TTS) <https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/tts/intro.html#>`_
-    * Spectrogram generation: Tacotron2, GlowTTS, TalkNet, FastPitch, FastSpeech2, Mixer-TTS, Mixer-TTS-X
-    * Vocoders: WaveGlow, SqueezeWave, UniGlow, MelGAN, HiFiGAN, UnivNet
-    * End-to-end speech generation: FastPitch_HifiGan_E2E, FastSpeech2_HifiGan_E2E, VITS
-    * `NGC collection of pre-trained TTS models. <https://ngc.nvidia.com/catalog/collections/nvidia:nemo_tts>`_
+* Text-to-Speech Synthesis (TTS):
+    * `Documentation <https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/tts/intro.html#>`_
+    * Mel-Spectrogram generators: FastPitch, SSL FastPitch, Mixer-TTS/Mixer-TTS-X, RAD-TTS, Tacotron2
+    * Vocoders: HiFiGAN, UnivNet, WaveGlow
+    * End-to-End Models: VITS
+    * `Pre-trained Model Checkpoints in NVIDIA GPU Cloud (NGC) <https://ngc.nvidia.com/catalog/collections/nvidia:nemo_tts>`_
 * `Tools <https://github.com/NVIDIA/NeMo/tree/stable/tools>`_
     * `Text Processing (text normalization and inverse text normalization) <https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/nlp/text_normalization/intro.html>`_
     * `CTC-Segmentation tool <https://docs.nvidia.com/deeplearning/nemo/user-guide/docs/en/main/tools/ctc_segmentation.html>`_