Update iconloaderlib min_sdk_version to 26. am: e5430492 am: fdfdc3a0 am: 9bb10e0d am: 12d92313

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/libs/systemui/+/15602014

Change-Id: I49f5f35420e76de9fcf18950c20c8726fb16048f