Update iconloaderlib min_sdk_version to 26. am: e5430492 am: fdfdc3a0 am: f6b34e2f am: 6e5332af

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

Change-Id: Ib5e37d146773de2b0ba7efb2d78607e4e460189b