Fix newly introduced warnings in LifetimeDependenceScopeFixup

Author: meg-gupta

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LifetimeDependenceScopeFixup.swift

@@ -194,19 +194,7 @@ private func createEndCOWMutationIfNeeded(lifetimeDep: LifetimeDependence, _ con
       }
       scoped = beginApply
     // None of the below cases can generate a mutable address.
-    case let .owned:
-      fallthrough
-    case let .borrowed:
-      fallthrough
-    case let .local:
-      fallthrough
-    case let .initialized:
-      fallthrough
-    case let .caller:
-      fallthrough
-    case let .global:
-      fallthrough
-    case let .unknown:
+    case .owned, .borrowed, .local, .initialized, .caller, .global, .unknown:
       return
   }
 

SwiftCompilerSources/Sources/SIL/Builder.swift

@@ -582,6 +582,7 @@ public struct Builder {
     return notifyNew(endMutation.getAs(EndCOWMutationInst.self))
   }
 
+  @discardableResult
   public func createEndCOWMutationAddr(address: Value) -> EndCOWMutationAddrInst {
     let endMutation = bridged.createEndCOWMutationAddr(address.bridged)
     return notifyNew(endMutation.getAs(EndCOWMutationAddrInst.self))