java_module: Rename to java

I named this "java_module" to avoid confusion with app/src/main/java,
but there's no need to be so verbose.

build.sh

@@ -15,7 +15,7 @@ fi
 $HOME/code/android/sdk/ndk/21.4.7075529/ndk-build -j48 NDK_DEBUG=$debug_mode
 popd
 
-pushd java_module
+pushd java
 # Must always be release due to R8 requirement
 ./gradlew assembleRelease
 popd
@@ -29,6 +29,6 @@ done
 pushd magisk
 version="$(grep '^version=' module.prop  | cut -d= -f2)"
 rm -f "../safetynet-fix-$version.zip" classes.dex
-unzip "../java_module/app/build/outputs/apk/release/app-release.apk" "classes.dex"
+unzip "../java/app/build/outputs/apk/release/app-release.apk" "classes.dex"
 zip -r9 "../safetynet-fix-$version.zip" .
 popd