Update SAI submodule (sonic-net#1015)

Update SAI submodule v1.9 with the following fixes

7594e53 (HEAD, origin/v1.9) Skip brcm teardown assertion (sonic-net#1423) (sonic-net#1428)
0c33f4a [FIX]Fix the circular reference issue when build sai header py (sonic-net#1427)
7e0fc24 Add support for building under Doxygen 1.9.1 (sonic-net#1414) (sonic-net#1424)
8ecf3ef [Fix]Correct enum check on branch 1.9 (sonic-net#1418)
e2b2f39 Add Thrift 0.14.1 compatibility (sonic-net#1403) (sonic-net#1416)

Author: alexrallen