Fix README venv installation command and dotenv (elastic#63)

* Fix README venv installation command

* Fix dotenv command

Author: anuraaga

instrumentation/elastic-opentelemetry-instrumentation-openai/README.md

@@ -27,7 +27,7 @@ and `dotenv` (a portable way to load environment variables).
 ```
 python3 -m venv .venv
 source .venv/bin/activate
-pip install -r test-requirements.txt
+pip install -r dev-requirements.txt
 pip install python-dotenv[cli]
 ```
 
@@ -64,7 +64,7 @@ ollama pull all-minilm:33m
 Finally run the examples using [ollama.env](ollama.env) variables to point to Ollama instead of OpenAI:
 
 ```
-dotenv run -f ollama.env -- opentelemetry-instrument python examples/chat.py
+dotenv -f ollama.env run -- opentelemetry-instrument python examples/chat.py
 ```
 
 ### Instrumentation specific environment variable configuration