Update SK_IMAGE_VERSION to test RAW

Once https://codereview.chromium.org/1520403003/ lands, we can start
testing RAW images. I have already added RAW images to a folder named
v2/; this updates the version so the script (once written) will check
the new version.

Depends on skbug.com/4558

BUG=skia:4829
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1612113002

Review URL: https://codereview.chromium.org/1612113002
diff --git a/SK_IMAGE_VERSION b/SK_IMAGE_VERSION
index d00491f..0cfbf08 100644
--- a/SK_IMAGE_VERSION
+++ b/SK_IMAGE_VERSION
@@ -1 +1 @@
-1
+2