Remove extra spaces (#11283)

### Description
When I was reading the document, I found that some examples had extra
spaces and violated "Unexpected spaces around keyword / parameter equals
(E251)" in pep8. I removed these extra spaces.
  
### Tag maintainer
@eyurtsev 
### Twitter handle
[billvsme](https://twitter.com/billvsme)

docs/snippets/modules/agents/how_to/custom_llm_agent.mdx

@@ -36,7 +36,7 @@ Set up any tools the agent may want to use. This may be necessary to put in the
 search = SerpAPIWrapper()
 tools = [
     Tool(
-        name = "Search",
+        name="Search",
         func=search.run,
         description="useful for when you need to answer questions about current events"
     )

docs/snippets/modules/agents/how_to/custom_llm_chat_agent.mdx

@@ -51,7 +51,7 @@ SERPAPI_API_KEY = getpass()
 search = SerpAPIWrapper(serpapi_api_key=SERPAPI_API_KEY)
 tools = [
     Tool(
-        name = "Search",
+        name="Search",
         func=search.run,
         description="useful for when you need to answer questions about current events"
     )

docs/snippets/modules/agents/how_to/mrkl.mdx

@@ -13,7 +13,7 @@ db = SQLDatabase.from_uri("sqlite:///../../../../../notebooks/Chinook.db")
 db_chain = SQLDatabaseChain.from_llm(llm, db, verbose=True)
 tools = [
     Tool(
-        name = "Search",
+        name="Search",
         func=search.run,
         description="useful for when you need to answer questions about current events. You should ask targeted questions"
     ),

docs/snippets/modules/agents/how_to/mrkl_chat.mdx

@@ -9,7 +9,7 @@ db = SQLDatabase.from_uri("sqlite:///../../../../../notebooks/Chinook.db")
 db_chain = SQLDatabaseChain.from_llm(llm1, db, verbose=True)
 tools = [
     Tool(
-        name = "Search",
+        name="Search",
         func=search.run,
         description="useful for when you need to answer questions about current events. You should ask targeted questions"
     ),