docs: renumber to ADR-054

053 collided with the derived-condition-recovery ADR added to NVIDIA#1706 at 12:34 UTC,
eight minutes after this branch took the number. Neither is merged and the timing
was effectively simultaneous, so this moves rather than contests it: NVIDIA#1706 is a
51-file feature PR under review and this is a single file, so renumbering here is
the cheaper side.

Signed-off-by: Lonnie Friedman <lfriedman@together.ai>

Author: lfriedman-netllama

…/designs/053-changestream-lag-metrics.md …/designs/054-changestream-lag-metrics.mddocs/designs/053-changestream-lag-metrics.md renamed to docs/designs/054-changestream-lag-metrics.md docs/designs/053-changestream-lag-metrics.md renamed to docs/designs/054-changestream-lag-metrics.md

@@ -1,4 +1,4 @@
-# ADR-053: `Observability` — change stream consumer lag metrics
+# ADR-054: `Observability` — change stream consumer lag metrics
 
 ## Table of contents