Update text analyzer documentation clarifying the example

[kolchfa-aws]

Corrects documentation for the edge_ngram and ngram tokenizers, which previously suggested that both tokenizers parse strings into words by default. In fact, tokenizers treat the entire input as a single token unless configured with token_chars. Updated descriptions to explain this default behavior and show that configuration is required for word-based parsing. Updated the edge_ngram example to demonstrate configured behavior.

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