Fix typo

vendor/botan/bindings/botan.odin

@@ -142,7 +142,7 @@ fpe_t                :: ^fpe_struct
 
 when ODIN_OS == .Windows {
     foreign import botan_lib "botan.lib"
-} else  ODIN_OS == .Darwin {
+} else when ODIN_OS == .Darwin {
     foreign import botan_lib "system:botan-3"
 } else {
     foreign import botan_lib "system:botan-2"