DOCS: Fixed small errors in the text and made code format more consistent (#5664)

## Why are these changes needed?

Fix minor issues in docs:
- probably editing left over
- typo
- code formatting inconsistency

## Related issue number

N/A

## Checks

- [ X] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [ X] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [ X] I've made sure all auto checks have passed.

Co-authored-by: Jack Gerrits <jackgerrits@users.noreply.github.com>

python/packages/autogen-core/docs/src/user-guide/core-user-guide/design-patterns/group-chat.ipynb

@@ -358,7 +358,7 @@
     "The group chat manager's constructor takes a list of participants' topic types\n",
     "as an argument.\n",
     "To prompt the next speaker to work, \n",
-    "the it publishes a `RequestToSpeak` message to the next participant's topic.\n",
+    "the `GroupChatManager` agent publishes a `RequestToSpeak` message to the next participant's topic.\n",
     "\n",
     "In this example, we also make sure the group chat manager always picks a different\n",
     "participant to speak next, by keeping track of the previous speaker.\n",
@@ -457,7 +457,7 @@
    "source": [
     "## Creating the Group Chat\n",
     "\n",
-    "To set up the group chat, we create an {py:class}`~autogen_core.SingleThreadedAgentRuntime`\n",
+    "To set up the group chat, we create a {py:class}`~autogen_core.SingleThreadedAgentRuntime`\n",
     "and register the agents' factories and subscriptions.\n",
     "\n",
     "Each participant agent subscribes to both the group chat topic as well as its own\n",