docs: enhance decorator documentation and update LLM syntax

docs/concepts/planning.mdx

@@ -31,7 +31,7 @@ From this point on, your crew will have planning enabled, and the tasks will be
 
 #### Planning LLM
 
-Now you can define the LLM that will be used to plan the tasks. You can use any ChatOpenAI LLM model available.
+Now you can define the LLM that will be used to plan the tasks. 
 
 When running the base case example, you will see something like the output below, which represents the output of the `AgentPlanner` 
 responsible for creating the step-by-step logic to add to the Agents' tasks.
@@ -39,7 +39,6 @@ responsible for creating the step-by-step logic to add to the Agents' tasks.
 <CodeGroup>
 ```python Code
 from crewai import Crew, Agent, Task, Process
-from langchain_openai import ChatOpenAI
 
 # Assemble your crew with planning capabilities and custom LLM
 my_crew = Crew(
@@ -47,7 +46,7 @@ my_crew = Crew(
     tasks=self.tasks,
     process=Process.sequential,
     planning=True,
-    planning_llm=ChatOpenAI(model="gpt-4o")
+    planning_llm="gpt-4o"
 )
 
 # Run the crew

docs/concepts/processes.mdx

@@ -23,9 +23,7 @@ Processes enable individual agents to operate as a cohesive unit, streamlining t
 To assign a process to a crew, specify the process type upon crew creation to set the execution strategy. For a hierarchical process, ensure to define `manager_llm` or `manager_agent` for the manager agent.
 
 ```python
-from crewai import Crew
-from crewai.process import Process
-from langchain_openai import ChatOpenAI
+from crewai import Crew, Process
 
 # Example: Creating a crew with a sequential process
 crew = Crew(
@@ -40,7 +38,7 @@ crew = Crew(
     agents=my_agents,
     tasks=my_tasks,
     process=Process.hierarchical,
-    manager_llm=ChatOpenAI(model="gpt-4")
+    manager_llm="gpt-4o"
     # or
     # manager_agent=my_manager_agent
 )