Merge pull request #1303 from rudkx/fix-more-iuo-casts

Fix a couple more IUOs that were supposed to be banned by SE-0054.

Author: rudkx

Foundation/NSTimeZone.swift

@@ -99,7 +99,7 @@ open class NSTimeZone : NSObject, NSCopying, NSSecureCoding, NSCoding {
 
     public convenience init?(abbreviation: String) {
         let abbr = abbreviation._cfObject
-        guard let name = unsafeBitCast(CFDictionaryGetValue(CFTimeZoneCopyAbbreviationDictionary(), unsafeBitCast(abbr, to: UnsafeRawPointer.self)), to: NSString!.self) else {
+        guard let name = unsafeBitCast(CFDictionaryGetValue(CFTimeZoneCopyAbbreviationDictionary(), unsafeBitCast(abbr, to: UnsafeRawPointer.self)), to: NSString?.self) else {
             return nil
         }
         self.init(name: name._swiftObject , data: nil)

Foundation/ProcessInfo.swift

@@ -88,7 +88,7 @@ open class ProcessInfo: NSObject {
         }
 
         let productVersionKey = unsafeBitCast(_kCFSystemVersionProductVersionKey, to: UnsafeRawPointer.self)
-        guard let productVersion = unsafeBitCast(CFDictionaryGetValue(systemVersionDictionary, productVersionKey), to: NSString!.self) else {
+        guard let productVersion = unsafeBitCast(CFDictionaryGetValue(systemVersionDictionary, productVersionKey), to: NSString?.self) else {
             return OperatingSystemVersion(majorVersion: fallbackMajor, minorVersion: fallbackMinor, patchVersion: fallbackPatch)
         }