yuzu/main: Tidy up the error dialog string in OnTransferableShaderCacheOpenFile()

Rather than scream that the file doesn't exist, we can clearly state
what specifically doesn't exist, to avoid ambiguity, and make it easier
to understand for non-primary English speakers/readers.

src/yuzu/main.cpp

@@ -1087,7 +1087,6 @@ void GMainWindow::OnGameListOpenFolder(u64 program_id, GameListOpenTarget target
 void GMainWindow::OnTransferableShaderCacheOpenFile(u64 program_id) {
     ASSERT(program_id != 0);
 
-    const QString open_target = QStringLiteral("Transferable Shader Cache");
     const QString tranferable_shader_cache_folder_path =
         QString::fromStdString(FileUtil::GetUserPath(FileUtil::UserPath::ShaderDir)) + "opengl" +
         DIR_SEP + "transferable";
@@ -1097,8 +1096,8 @@ void GMainWindow::OnTransferableShaderCacheOpenFile(u64 program_id) {
         QString::fromStdString(fmt::format("{:016X}.bin", program_id));
 
     if (!QFile::exists(transferable_shader_cache_file_path)) {
-        QMessageBox::warning(this, tr("Error Opening %1 File").arg(open_target),
-                             tr("File does not exist!"));
+        QMessageBox::warning(this, tr("Error Opening Transferable Shader Cache"),
+                             tr("A shader cache for this title does not exist."));
         return;
     }