fix: use Rust 1.90.0 for VectorChord v1.0.0 simd compilation

VectorChord v1.0.0 simd crate uses AVX-512 intrinsics that require
Rust >= 1.90.0 for target feature safety (RFC 3525). Same fix as
v1.1.0 but applied to the downgraded version.

Validated: Nix dry-run eval passes in Docker (linux/amd64).

Author: h0lybyte

nix/ext/vectorchord.nix

@@ -8,7 +8,7 @@
 let
   pname = "vchord";
   version = "1.0.0";
-  rustVersion = "1.88.0";
+  rustVersion = "1.90.0";
   pgrxVersion = "0.16.1";
 
   cargo = rust-bin.stable.${rustVersion}.default;