Allow sysroot 2.28 in CUDA 11 jobs. (#749)

This removes some special cases added in #745 around sysroot pinnings. Those were needed for CUDA 11.4 until a recent repodata patch. Thanks @jakirkham!

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - https://github.com/jakirkham

URL: #749

dependencies.yaml

@@ -56,16 +56,6 @@ dependencies:
               - gcc<14.0.0
       - output_types: conda
         matrices:
-          - matrix:
-              arch: x86_64
-              cuda: "11.[2456]"
-            packages:
-              - sysroot_linux-64==2.17
-          - matrix:
-              arch: aarch64
-              cuda: "11.[2456]"
-            packages:
-              - sysroot_linux-aarch64==2.17
           - matrix:
               arch: x86_64
             packages: