fix(diagrams): missing quotes for protocol negotiation diagram (#5751)

Description
---
adds missing quotes for protocol negotiation diagram

Motivation and Context
---

How Has This Been Tested?
---

What process can a PR reviewer use to test or verify this change?
---

<!-- Checklist -->
<!-- 1. Is the title of your PR in the form that would make nice release
notes? The title, excluding the conventional commit
tag, will be included exactly as is in the CHANGELOG, so please think
about it carefully. -->


Breaking Changes
---

- [x] None
- [ ] Requires data directory on base node to be deleted
- [ ] Requires hard fork
- [ ] Other - Please specify

<!-- Does this include a breaking change? If so, include this line as a
footer -->
<!-- BREAKING CHANGE: Description what the user should do, e.g. delete a
database, resync the chain -->

docs/src/diagrams/comms/protocol_negotiation.md

@@ -24,7 +24,7 @@ Messages are the tuple (length (u8), flags (u8), protocol_name (variable 255 (0x
 flowchart TD
 A[Start] --> B[1. New substream opened by remote peer]
 B --> C[2. PeerConnection starts ProtocolNegotiation]
-C --> D[3.⌛️ Inbound ProtocolNegotiation waits for bytes to read]
+C --> D["3.⌛️ Inbound ProtocolNegotiation waits for bytes to read"]
 D --> E["4. Read frame (len, flags, protocol_name)"]
 
 %% Optimistic