[TTS] Move Spanish polyphones from heteronym to dictionary
# What does this PR do ?

Spanish does not have heteronyms, only polyphones (eg. region-specific pronunciations of the same word). To make this clearer, I am removing the heteronyms file and placing the alternative pronunciations into the dictionary.

**Collection**: [TTS]

# Changelog 
- Delete es_ES and es_LA heteronym files
- Move words in heteronym files to pronunciation dictionary with multiple entries.

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