configure_graphics: Mark SPIR-V as Experimental, Mesa only

src/yuzu/configuration/configure_graphics.cpp

@@ -32,7 +32,7 @@ ConfigureGraphics::ConfigureGraphics(QWidget* parent)
 
     ui->backend->addItem(QStringLiteral("GLSL"));
     ui->backend->addItem(tr("GLASM (NVIDIA Only)"));
-    ui->backend->addItem(QStringLiteral("SPIR-V"));
+    ui->backend->addItem(QStringLiteral("SPIR-V (Experimental, Mesa Only)"));
 
     SetupPerGameUI();