docs(pep): stale status lines and a redundant Mermaid chain in pep.rst #2564

From the 2026-11-01 conventions audit, re-verified on 73add05a3. process.rst, "The PEP Discussion, Kept Current": pep.rst is the source of truth for where each wave stands. documentation.rst, "Mermaid for Flows": do not redraw a graph another page already has.

• Delivery Sequence (docs/source/contributing/pep.rst): DCCP is "blocked on :issue:2479 for its pseudo-header checksum". feat(protocols): add the IP_Pseudo pseudo-protocol for the IP pseudo-header (#2471) #2479 is a merged pull request; DCCP implementation, with the DCCP checksum over the IP pseudo-header #2489 is blocked on the checksum wave (ICMP/ICMPv6 checksum verification (deferred from #2446) #2470).
• "Done ahead of wave 2" (pep.rst, under "Delivery Sequence"): NETLINK, IPGRE, IP6GRE, IEEE80211_RADIOTAP and FRAD "have no dissector of their own, tracked as :issue:2460". pcapkit/protocols/link/frad.py, gre.py and netlink.py exist and Dissectors for non-ethertype ARPHRD types on LINUX_SLL/SLL2 (NETLINK/IPGRE/IP6GRE/802.11 radiotap/FRAD) #2460 is closed; only radiotap is missing, tracked by 802.11 radiotap dissector for IEEE80211_RADIOTAP on LINUX_SLL/SLL2 #2502.
• "Release Plan — 1.5.0 in Two Steps" (pep.rst): the .. mermaid:: draws push -> Unit Tests -> Vendor Update -> Create Release, which the sentence above it states and workflows.rst draws with the same node labels and edges.

Fix: correct both status lines and drop the graph. Discussion #106 carries neither stale line, so it needs no correction for them.
Blocked: #2528, #2542, #2543 and #2544 edit pep.rst; unblocks when all four merge (gh pr view <n> --json state -q .state prints MERGED).