Revert "Vulkan: Don't expose MSRTT on SwiftShader"

This reverts commit fb77afd3c7.

Reason for revert: Breaks ANGLE roll into Chromium:
https://chromium-review.googlesource.com/c/chromium/src/+/3253966/

Please follow the directions here to update the reference images:
https://chromium.googlesource.com/chromium/src/+/HEAD/docs/testing/web_test_expectations.md

Original change's description:
> Vulkan: Don't expose MSRTT on SwiftShader
>
> Emulating this extension on SwiftShader is neither useful nor efficient
> (on the contrary, it hurts performance (which is true for all non-tiling
> architectures)).  This extension was exposed purely to increase testing
> coverage, but is being disabled now as OOMs resulting from allocating
> the implict multisampled image is confusing Chrome.  Note that
> SwiftShader exposes only a limited amount of memory.
>
> Bug: chromium:1263046
> Change-Id: Ia69b7fc63804169431885352a8f637a95ab08bd0
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3251581
> Reviewed-by: Geoff Lang <geofflang@chromium.org>
> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>

Bug: chromium:1263046
Change-Id: I554df85109282db840ed6d2dbf0b153da5a7a98f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3254007
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Tim Van Patten <timvp@google.com>

src/libANGLE/renderer/vulkan/RendererVk.cpp

@@ -2729,17 +2729,13 @@ void RendererVk::initFeatures(DisplayVk *displayVk,
 
     // Feature disabled due to driver bugs:
     //
-    // - Swiftshader:
-    //   * Failure on mac: http://anglebug.com/4937
-    //   * OOM: http://crbug.com/1263046
+    // - Swiftshader on mac: http://anglebug.com/4937
     // - Intel on windows: http://anglebug.com/5032
     // - AMD on windows: http://crbug.com/1132366
-    //
-    // Note that emulation of GL_EXT_multisampled_render_to_texture is only really useful on tiling
-    // hardware, but is exposed on desktop platforms purely to increase testing coverage.
-    ANGLE_FEATURE_CONDITION(&mFeatures, enableMultisampledRenderToTexture,
-                            mFeatures.supportsMultisampledRenderToSingleSampled.enabled ||
-                                (!isSwiftShader && !(IsWindows() && (isIntel || isAMD))));
+    ANGLE_FEATURE_CONDITION(
+        &mFeatures, enableMultisampledRenderToTexture,
+        mFeatures.supportsMultisampledRenderToSingleSampled.enabled ||
+            !(IsApple() && isSwiftShader) && !(IsWindows() && (isIntel || isAMD)));
 
     // Currently we enable cube map arrays based on the imageCubeArray Vk feature.
     // TODO: Check device caps for full cube map array support. http://anglebug.com/5143