Rename `dimension:` parameter to `dimensions:` everywhere.

[Andrei Bondarev]

Description

"Dimensions" (plural) is clearer than "dimension". The reference is to the depth of the array, the number of dimensions in a vector.

Tasks

1. Rename the dimension: parameter to dimensions: everywhere. Example: https://github.com/patterns-ai-core/langchainrb/blob/main/lib/langchain/llm/cohere.rb#L18

[Paul Danelli]

This will likely be a breaking change so should be highlighted in any change docs released :)