Revert "swift-api-digester: initialize vector with a reasonable capacity." (#6184)

This did not resolve the test failure.

Author: nkcsgexi

test/api-digester/compare-dump.swift

@@ -1,3 +1,4 @@
+// REQUIRES: rdar://29591753
 // RUN: rm -rf %t.mod && mkdir -p %t.mod
 // RUN: rm -rf %t.sdk && mkdir -p %t.sdk
 // RUN: rm -rf %t.module-cache && mkdir -p %t.module-cache

test/api-digester/source-stability.swift

@@ -1,3 +1,4 @@
+// REQUIRES: rdar://29591753
 // REQUIRES: OS=macosx
 // RUN: rm -rf %S/tmp && mkdir %S/tmp && mkdir %S/tmp/module-cache && mkdir %S/tmp/dummy.sdk
 // RUN: %api-digester -dump-sdk -module Swift -o %S/tmp/current-stdlib.json -module-cache-path %S/tmp/module-cache -sdk %S/tmp/dummy.sdk -swift-version 3

tools/swift-api-digester/swift-api-digester.cpp

@@ -166,12 +166,10 @@ typedef std::map<NodePtr, NodePtr> ParentMap;
 typedef std::vector<NodePtr> NodeVector;
 
 class SDKContext {
-  unsigned SIZE = 1024 * 1024;
   llvm::StringSet<> TextData;
   std::vector<std::unique_ptr<SDKNode>> OwnedNodes;
 
 public:
-  SDKContext() : OwnedNodes(SIZE) {}
   SDKNode* own(SDKNode *Node) {
     assert(Node);
     OwnedNodes.emplace_back(Node);