Updating androidx_multiplatform.sh to call androidx.sh
Updating androidx_multiplatform.sh to call androidx.sh

So we don't have to update it if we make changes to androidx.sh

Bug: 184959797
Test: Run `./busytown/androidx_multiplatform.sh` and see that it says:
  Running OUT_DIR=../../out DIST_DIR=../../out/dist ANDROID_HOME=../../prebuilts/fullsdk-linux ./gradlew --ci buildOnServer checkExternalLicenses listTaskOutputs validateAllProperties --profile -Pandroidx.compose.multiplatformEnabled=true

Change-Id: Id823b1c2afb4de632a3c9f2b008ff27d34c9279f

AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx,AndroidX/androidx