SkQP: relax test radial_gradient_precision

motivation: this is a bad test in that low-precision drivers will give
completely different results.

The jitter test might have caught this, but  I ran the jitter test with
the 8888 backend, which has high precision.

Bug: skia:8857
Change-Id: I7111ca34df7e510a1dbb591b1161b32912c82fe0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/200926
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
diff --git a/platform_tools/android/apps/skqp/src/main/assets/skqp/rendertests.txt b/platform_tools/android/apps/skqp/src/main/assets/skqp/rendertests.txt
index 12e69a9..235a34f 100644
--- a/platform_tools/android/apps/skqp/src/main/assets/skqp/rendertests.txt
+++ b/platform_tools/android/apps/skqp/src/main/assets/skqp/rendertests.txt
@@ -532,7 +532,7 @@
 radial_gradient3_nodither,0
 radial_gradient4,-1
 radial_gradient4_nodither,-1
-radial_gradient_precision,0
+radial_gradient_precision,-1
 readpixels,0
 readpixelscodec,0
 readpixelspicture,0