Removing @available tags

...NLP Internal Protocols/SNLPCorpus + Text Processing.swift

Sources/SwiftNLP/0. SNLP Internal Protocols/SNLPCorpus.swift

.../SwiftNLP/0. SNLP Internal Protocols/SNLPDictionary.swift

.../SwiftNLP/0. SNLP Internal Protocols/SNLPTopicModel.swift

Sources/SwiftNLP/1. Data Collection/20 Newsgroups.swift

...ftNLP/1. Data Collection/Top 20k Subreddit Download.swift

Sources/SwiftNLP/2. Embeddings/BoWCorpus.swift

Sources/SwiftNLP/2. Embeddings/KeyedVectorCorpus.swift

Sources/SwiftNLP/2. Embeddings/KeyedVectorDictionary.swift

Sources/SwiftNLP/2. Embeddings/SIMDCorpus.swift