Fix lifetime inference with older .swiftinterface files.

This was fix was accidentally not include in the previous commit,
which breaks older .swiftinterface files without it:

commit 75ba7a8
Merge: befc15e d41c4d4
Author: Andrew Trick <[email protected]>
Date:   Wed Mar 19 18:22:35 2025

    Merge pull request #80064 from atrick/lifetime-inference

    LifetimeDependence: implement strict type checking

Author: atrick

lib/AST/LifetimeDependence.cpp

@@ -334,7 +334,7 @@ class LifetimeDependenceChecker {
     // TODO: remove this check once all compilers that are rev-locked to the
     // stdlib print the 'copy' dependence kind in the interface (Aug '25)
     if (auto *sf = afd->getParentSourceFile()) {
-      if (sf->Kind == SourceFileKind::SIL) {
+      if (sf->Kind == SourceFileKind::Interface) {
         return true;
       }
     }

test/SIL/Parser/lifetime_dependence.sil

@@ -18,7 +18,7 @@ struct BufferView : ~Escapable {
 @lifetime(borrow x) 
 func derive(_ x: borrowing BufferView) -> BufferView
 
-@lifetime(x) 
+@lifetime(copy x)
 func consumeAndCreate(_ x: consuming BufferView) -> BufferView
 
 sil hidden [unsafe_nonescapable_result] @bufferviewinit1 : $@convention(method) (UnsafeRawBufferPointer, @thin BufferView.Type) -> @owned BufferView {