Remove imports of Foundation(Essentials|Internationalization|) when TestSupport is imported

TestSupport has `@_exported` imports for those modules.

Author: ahoppen

Tests/FoundationEssentialsTests/AttributedString/AttributedStringCOWTests.swift

@@ -14,12 +14,6 @@
 import TestSupport
 #endif
 
-#if FOUNDATION_FRAMEWORK
-import Foundation
-#else
-import FoundationEssentials
-#endif
-
 extension AttributedStringProtocol {
     fileprivate mutating func genericSetAttribute() {
         self.testInt = 3

Tests/FoundationEssentialsTests/AttributedString/AttributedStringTests.swift

@@ -14,10 +14,6 @@
 import TestSupport
 #endif
 
-#if canImport(FoundationEssentials)
-import FoundationEssentials
-#endif // FOUNDATION_FRAMEWORK
-
 #if FOUNDATION_FRAMEWORK
 @_spi(AttributedString) import Foundation
 // For testing default attribute scope conversion