postgresql_18: 18.0 -> 18.1

Release Notes:
https://github.com/postgres/postgres/blob/4b324845ba5d24682b9b3708a769f00d160afbd7/doc/src/sgml/release-18.sgml

Fixes:
CVE-2025-12817
CVE-2025-12818

pkgs/servers/sql/postgresql/18.nix

@@ -1,7 +1,9 @@
 import ./generic.nix {
-  version = "18.0";
-  rev = "refs/tags/REL_18_0";
-  hash = "sha256-xA6gbJe4tIV9bYRFrdI4Rfy20ZwTkvyyjt7ZxvCFEec=";
+  version = "18.1";
+  # TODO: Move back to tag, when they appear upstream:
+  # rev = "refs/tags/REL_18_1";
+  rev = "4b324845ba5d24682b9b3708a769f00d160afbd7";
+  hash = "sha256-cZA2hWtr5RwsUrRWkvl/yvUzFPSfdtpyAKGXfrVUr0g=";
   muslPatches = {
     dont-use-locale-a = {
       url = "https://git.alpinelinux.org/aports/plain/main/postgresql17/dont-use-locale-a-on-musl.patch?id=d69ead2c87230118ae7f72cef7d761e761e1f37e";

pkgs/servers/sql/postgresql/generic.nix

@@ -426,12 +426,6 @@ let
       ]
       ++ lib.optionals (stdenv'.hostPlatform.isDarwin && olderThan "16") [
         ./patches/export-dynamic-darwin-15-.patch
-      ]
-      ++ lib.optionals (atLeast "18") [
-        (fetchpatch2 {
-          url = "https://github.com/postgres/postgres/commit/a48d1ef58652229521ba4b5070e19f857608b22e.patch";
-          hash = "sha256-3FKQS1Vpu+p6z6c1GWs6GlrLl2Bgm9paEU/z81LrEus=";
-        })
       ];
 
       installTargets = [ "install-world" ];