Move ComposeContentTestRuleExt to SpaLibTestUtils

To use it in SpaTests in the future.

Bug: 259520506
Test: Unit test
Change-Id: Ic5ad78be4e04451cf317a70dfd615293565b488d
diff --git a/packages/SettingsLib/Spa/tests/Android.bp b/packages/SettingsLib/Spa/tests/Android.bp
index dcfc171..69740058 100644
--- a/packages/SettingsLib/Spa/tests/Android.bp
+++ b/packages/SettingsLib/Spa/tests/Android.bp
@@ -27,13 +27,10 @@
     static_libs: [
         "SpaLib",
         "SpaLibTestUtils",
-        "androidx.test.runner",
-        "androidx.test.ext.junit",
         "androidx.compose.runtime_runtime",
-        "androidx.compose.ui_ui-test-junit4",
-        "androidx.compose.ui_ui-test-manifest",
+        "androidx.test.ext.junit",
+        "androidx.test.runner",
         "mockito-target-minus-junit4",
-        "truth-prebuilt",
     ],
     kotlincflags: ["-Xjvm-default=all"],
     min_sdk_version: "31",