Fix ShaderTest to fetch both of it's docs (#1956)

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# Based on PR #1886

## Chain of upstream PRs as of 2024-12-30

* PR #1886:
  `main` ← `feature/protoconv`

  * **PR #1956 (THIS ONE)**:
    `feature/protoconv` ← `wb/froeht/fix-shader`

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integration-tests/validation/src/testDebug/kotlin/com/android/designcompose/testapp/validation/ShaderTest.kt

@@ -27,6 +27,7 @@ import com.android.designcompose.test.internal.designComposeRoborazziRule
 import com.android.designcompose.test.waitForContent
 import com.android.designcompose.testapp.common.InterFontTestRule
 import com.android.designcompose.testapp.validation.examples.BrushFromShaderPluginTest
+import com.android.designcompose.testapp.validation.examples.BrushFromShaderPluginTestDoc
 import com.android.designcompose.testapp.validation.examples.CustomBrushTest
 import com.android.designcompose.testapp.validation.examples.CustomBrushTestDoc
 import org.junit.Before
@@ -70,6 +71,9 @@ class ShaderTest {
     fun shaderPluginBrush() {
         with(composeTestRule) {
             setContent { BrushFromShaderPluginTest() }
+            liveUpdateTestRule.performLiveFetch()
+            composeTestRule.waitForContent(BrushFromShaderPluginTestDoc.javaClass.name)
+
             captureRootRoboImage("ShaderPluginBrush_${Build.VERSION.SDK_INT}")
         }
     }