Remove searching of Xcode private paths in build

Summary:
This was needed a while back when we weak-linked particular frameworks.

Since then we've removed the need to do this:
1) There's no weak-linking of any Xcode frameworks. All Xcode frameworks are linked at runtime, as such they don't need to be referenced in the build.
2) Headers for any of Xcode's private libraries are resident in `PrivateHeaders`, part of the project.

This also breaks test targets in Xcode 13.2 since the search path for XCTest.framework is overridden. The Framework doesn't contain headers anymore:

```
note: did not find header 'XCTest.h' in framework 'XCTest' (loaded from '/Applications/xcode_13_2_1.app/Contents/SharedFrameworks'
``

Reviewed By: jbardini

Differential Revision: D33581989

fbshipit-source-id: efe2475b465cb9a4112ca200d5564efbd13ab891

Configuration/Shared.xcconfig

@@ -55,15 +55,9 @@ GCC_WARN_UNUSED_VALUE = YES
 GCC_WARN_UNUSED_VARIABLE = YES
 ONLY_ACTIVE_ARCH = YES
 
-// Inferred Directories. Important for the linker to be able to find and weak-link private symbols.
-APPLE_FRAMEWORKS_DIR = $(DEVELOPER_DIR)/../Frameworks
-APPLE_OTHER_FRAMEWORKS_DIR = $(DEVELOPER_DIR)/../OtherFrameworks
-APPLE_PLUGINS_DIR = $(DEVELOPER_DIR)/../PlugIns
-APPLE_SHARED_FRAMEWORKS_DIR = $(DEVELOPER_DIR)/../SharedFrameworks
-
 // Search Paths for Frameworks & Headers
 ALWAYS_SEARCH_USER_PATHS = NO
-FRAMEWORK_SEARCH_PATHS = $(inherited) $(APPLE_FRAMEWORKS_DIR) $(APPLE_PLUGINS_DIR) $(APPLE_OTHER_FRAMEWORKS_DIR) $(APPLE_SHARED_FRAMEWORKS_DIR) $(DEVELOPER_LIBRARY_DIR)/PrivateFrameworks $(SDKROOT)/System/Library/PrivateFrameworks /Library/Developer/PrivateFrameworks
+FRAMEWORK_SEARCH_PATHS = $(inherited) $(DEVELOPER_LIBRARY_DIR)/PrivateFrameworks $(SDKROOT)/System/Library/PrivateFrameworks /Library/Developer/PrivateFrameworks
 HEADER_SEARCH_PATHS = $(inherited) $(SRCROOT)/PrivateHeaders
 
 // SDK & OS Versions