Update sample.json

Author: jimmytwei

DirectProgramming/C++SYCL/VisualizedSamples/VisualMandlebrot/sample.json

@@ -11,7 +11,7 @@
   "ciTests": {
 	"linux": [{
 		"steps": [
-			"apt-get install libsdl2-dev",
+			"apt-get install -y libsdl2-dev",
 			"mkdir build",
       			"cd build",
 			"cmake ..",