change build type, remove example with product flavor

docs/android-build-variants.md

@@ -19,23 +19,8 @@ To ensure Flaker handles multiple variants correctly in your project, you should
         buildTypes {
             release {
             }
-            stage {
-                matchingFallbacks = ['debug', 'qa', 'release']
-            }
-        }
-    }
-```
-
-#### 2) Product Flavor
-```kotlin
-    android {
-        productFlavors {
-            create("paid") {
-                dimension = "tier"
-            }
-            create("free") {
-                dimension = "tier"
-                matchingFallbacks += listOf("demo", "trial")
+            qa {
+                matchingFallbacks = ['debug', 'release']
             }
         }
     }