chore: shuffle a bit to match what is needed for various versions

Author: samrose

flake.nix

@@ -131,6 +131,7 @@
         # go through the upstream release engineering process.
         ourExtensions = [
           ./nix/ext/rum.nix
+          ./nix/ext/timescaledb.nix
           ./nix/ext/pgroonga.nix
           ./nix/ext/index_advisor.nix
           ./nix/ext/wal2json.nix
@@ -216,7 +217,6 @@
             postgresql = getPostgresqlPackage version;
             extensions = if version == "15"
               then ourExtensions ++ [
-                ./nix/ext/timescaledb.nix
                 ./nix/ext/timescaledb-2.9.1.nix
               ]
               else ourExtensions;