Fix tests by removing side effect in getter

While setting up the test CurrentAppContect, we use OWSTemporaryDirectory which in turn
recursively references CurrentAppContext, which crashes.

Clearing temp directories on every activation is sufficient.

SignalServiceKit/src/Util/OWSFileSystem.m

@@ -348,14 +348,6 @@ NSString *OWSTemporaryDirectory(void)
         dirPath = [NSTemporaryDirectory() stringByAppendingPathComponent:dirName];
         BOOL success = [OWSFileSystem ensureDirectoryExists:dirPath fileProtectionType:NSFileProtectionComplete];
         OWSCAssert(success);
-
-        // On launch, clear old temp directories.
-        //
-        // NOTE: ClearOldTemporaryDirectoriesSync() will call this function
-        // OWSTemporaryDirectory(), but there's no risk of deadlock;
-        // ClearOldTemporaryDirectories() calls ClearOldTemporaryDirectoriesSync()
-        // after a long delay.
-        ClearOldTemporaryDirectories();
     });
     return dirPath;
 }