SF: set highp on outTexCoords

On implementations that use half floats for outTexCoords, the precision
is not enough when the layer is > 1024 in either dimension.

Bug: 253540001
Test: screencap, CTS

Change-Id: Ic712454b04e58cb93334a90377cacf013734a95a
diff --git a/libs/renderengine/gl/ProgramCache.cpp b/libs/renderengine/gl/ProgramCache.cpp
index 5ff9240..f7f2d54 100644
--- a/libs/renderengine/gl/ProgramCache.cpp
+++ b/libs/renderengine/gl/ProgramCache.cpp
@@ -601,7 +601,7 @@
     }
 
     if (needs.hasTextureCoords()) {
-        fs << "varying vec2 outTexCoords;";
+        fs << "varying highp vec2 outTexCoords;";
     }
 
     if (needs.hasRoundedCorners()) {