fix(core): Don't apply Windows file transfer rename on other platforms

Filename cleaning was originally introduced for Windows
https://github.com/qTox/qTox/issues/1304. It's unneeded on other platforms, so
leave file names as they're sent there.

Fix #5242

src/core/corefile.cpp

@@ -330,7 +330,7 @@ void CoreFile::onFileReceiveCallback(Tox* tox, uint32_t friendId, uint32_t fileI
             tox_file_control(tox, friendId, fileId, TOX_FILE_CONTROL_CANCEL, nullptr);
             emit core->friendAvatarRemoved(core->getFriendPublicKey(friendId));
             return;
-        } else {
+        }
         if (!ToxClientStandards::IsValidAvatarSize(filesize)) {
             qWarning() <<
                 QString("Received avatar request from %1 with size %2.").arg(friendId).arg(filesize) +
@@ -347,7 +347,7 @@ void CoreFile::onFileReceiveCallback(Tox* tox, uint32_t friendId, uint32_t fileI
         emit core->fileAvatarOfferReceived(friendId, fileId, avatarBytes, filesize);
         return;
     }
-    } else {
+    #ifdef Q_OS_WIN
     const auto cleanFileName = CoreFile::getCleanFileName(filename.getQString());
     if (cleanFileName != filename.getQString()) {
         qDebug() << QStringLiteral("Cleaned filename");
@@ -356,8 +356,8 @@ void CoreFile::onFileReceiveCallback(Tox* tox, uint32_t friendId, uint32_t fileI
     } else {
         qDebug() << QStringLiteral("filename already clean");
     }
+    #endif
     qDebug() << QString("Received file request %1:%2 kind %3").arg(friendId).arg(fileId).arg(kind);
-    }
 
     ToxFile file{fileId, friendId, filename.getBytes(), "", filesize, ToxFile::RECEIVING};
     file.fileKind = kind;