Revert "SILGen: Explicitly make fragile entities public when -sil-serialize-all is on"

This commit caused link failures across several stdlib tests.

This reverts commit 672356047d.

lib/SIL/SILDeclRef.cpp

@@ -324,15 +324,8 @@ SILLinkage SILDeclRef::getLinkage(ForDefinition_t forDefinition) const {
       if (isa<ClangModuleUnit>(derivedFor->getModuleScopeContext()))
         return ClangLinkage;
   }
-
-  // If the module is being built with -sil-serialize-all, everything has
-  // to have public linkage.
-  if (moduleContext->getParentModule()->getResilienceStrategy()
-      == ResilienceStrategy::Fragile) {
-    return (forDefinition ? SILLinkage::Public : SILLinkage::PublicExternal);
-  }
-
-  // Otherwise, linkage is determined by accessibility at the AST level.
+  
+  // Otherwise, we have external linkage.
   switch (d->getEffectiveAccess()) {
     case Accessibility::Private:
       return (forDefinition ? SILLinkage::Private : SILLinkage::PrivateExternal);