Update README.md (Typo "Azure Open AI"→"Azure OpenAI")

[hyoshioka0128]

Purpose

• Typo "Azure Open AI"→"Azure OpenAI"
• https://github.com/Azure-Samples/cosmosdb-chatgpt/blob/main/README.md
• #PingMSFTDocs

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[x] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information