fix(transport): rename local max to avoid shadowing builtin

revive's redefines-builtin-id flags the local variable named max in
the LRU eviction loop, which shadows the Go 1.21 builtin. Rename it to
limit; no behavior change.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 4959e1f9-f8e6-4e97-a487-f395a0123c79