SILGen: Remove triplesAreValidForZippering() assert.

This assert was correctly catching the fact that `-target-variant` is not being
normalized at the same time as `-target` when building arm64e modules from
swiftinterface. That should be fixed, but at the moment it isn't causing any
concrete harm and the assertion fails when building against the SDKs included
with the latest Xcode 16 betas.

Resolves rdar://133020098.

lib/Serialization/SerializedModuleLoader.cpp

@@ -1323,6 +1323,7 @@ bool swift::extractCompilerFlagsFromInterface(
   // we have loaded a Swift interface from a different-but-compatible
   // architecture slice. Use the compatible subarchitecture.
   for (unsigned I = 1; I < SubArgs.size(); ++I) {
+    // FIXME: Also fix up -target-variant (rdar://135322077).
     if (strcmp(SubArgs[I - 1], "-target") != 0) {
       continue;
     }