[Docs] Fix broken list rendering of Instrumentation in the README

This PR fixes the broken rendering of the following list:
https://github.com/modelcontextprotocol/ruby-sdk/tree/v0.2.0?tab=readme-ov-file#instrumentation

Author: koic

README.md

@@ -541,12 +541,13 @@ end
 ```
 
 The data contains the following keys:
-`method`: the method called, e.g. `ping`, `tools/list`, `tools/call` etc
-`tool_name`: the name of the tool called
-`prompt_name`: the name of the prompt called
-`resource_uri`: the uri of the resource called
-`error`: if looking up tools/prompts etc failed, e.g. `tool_not_found`
-`duration`: the duration of the call in seconds
+
+- `method`: the method called, e.g. `ping`, `tools/list`, `tools/call` etc
+- `tool_name`: the name of the tool called
+- `prompt_name`: the name of the prompt called
+- `resource_uri`: the uri of the resource called
+- `error`: if looking up tools/prompts etc failed, e.g. `tool_not_found`
+- `duration`: the duration of the call in seconds
 
 `tool_name`, `prompt_name` and `resource_uri` are only populated if a matching handler is registered.
 This is to avoid potential issues with metric cardinality