feat: Removes unused files.

Sources/ApiController/Extensions/Double+ensurePositive.swift

@@ -1,9 +0,0 @@
-import Foundation
-
-extension Double {
-
-  func ensurePostive() -> Self {
-    if self < 0 { return self * -1 }
-    return self
-  }
-}

Sources/ApiController/Extensions/HVACSystemPerformance.swift

@@ -85,8 +85,4 @@ public extension HVACSystemPerformance.Request {
       throw ValidationError(message: "System size should be greater than 0.")
     }
   }
-
-  struct ValidationError: Error {
-    let message: String
-  }
 }