Rename dimension parameter to dimensions everywhere

[mattlindsey]

Completes #575

[mattlindsey]

@andreibondarev I think this is ready, but check that the last Ollama rspec test is OK.
Instead of generating a new VCR fixture, I had to rename the existing one, since I get the following error otherwise, even though ollama is running using ollama serve:

Failures:

  1) Langchain::LLM::Ollama#default_dimensionss returns size of tinydolphin embeddings
     Failure/Error:
       response = client.post("api/embeddings") do |req|
         req.body = parameters
       end

     Faraday::ResourceNotFound:
       the server responded with status 404
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/response/raise_error.rb:22:in `on_complete'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/middleware.rb:18:in `block in call'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/response.rb:42:in `on_complete'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/middleware.rb:17:in `call'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/middleware.rb:17:in `call'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/middleware.rb:17:in `call'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/rack_builder.rb:152:in `build_response'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/connection.rb:444:in `run_request'
     # /Users/mattlindsey/.rvm/gems/ruby-3.2.2/gems/faraday-2.9.0/lib/faraday/connection.rb:280:in `post'
     # ./lib/langchain/llm/ollama.rb:242:in `embed'
     # ./lib/langchain/llm/ollama.rb:48:in `block in default_dimensions'
     # ./lib/langchain/llm/ollama.rb:47:in `fetch'
     # ./lib/langchain/llm/ollama.rb:47:in `default_dimensions'
     # ./spec/langchain/llm/ollama_spec.rb:116:in `block (3 levels) in <top (required)>'
     # ./spec/support/vcr.rb:26:in `block (2 levels) in <top (required)>'

Finished in 2.28 seconds (files took 1.18 seconds to load)
408 examples, 1 failure, 3 pending

[andreibondarev]

@mattlindsey Looks good!