Match dev shell hint to the documented build commands

Drops the unit-test hint, since the test sources do not compile upstream.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

flake.nix

@@ -55,8 +55,8 @@
             shellHook = ''
               echo "sdk.dir=$ANDROID_HOME" > local.properties
               echo "FatihsMG4 dev shell — JDK $(java -version 2>&1 | head -1 | cut -d'"' -f2), SDK at $ANDROID_HOME"
-              echo "  ./gradlew assembleStableDebug    build a debug APK"
-              echo "  ./gradlew testStableDebugUnitTest  run unit tests"
+              echo "  ./gradlew assembleStableDebug     # debug APK"
+              echo "  ./gradlew assembleUnstableDebug   # build that can update itself (OTA)"
             '';
           };
         });