[mlir][ArmSME] Remove dependency on a non-existing target (nfc)

Sending this one without a review - as `MLIRArmSMEIncGen` is not defined
anywhere, dependency on that target is clearly bogus.

Author: banach-space

mlir/lib/Dialect/ArmSME/IR/CMakeLists.txt

@@ -5,7 +5,6 @@ add_mlir_dialect_library(MLIRArmSMEDialect
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/ArmSME
 
   DEPENDS
-  MLIRArmSMEIncGen
   MLIRArmSMEAttrDefsIncGen
 
   LINK_LIBS PUBLIC