[Assignment Tracking] Fix tests for buildbot failure

Follow-up for 4ece507 (D142027).

Assignment Tracking Analysis now always runs and is skipped internally if
assignment tracking is disabled. Update these tests to expect to see the
pass run.

Buildbot failure: https://lab.llvm.org/buildbot/#/builders/216/builds/16085

Author: OCHyams

llvm/test/CodeGen/X86/O0-pipeline.ll

@@ -35,6 +35,7 @@
 ; CHECK-NEXT:       Safe Stack instrumentation pass
 ; CHECK-NEXT:       Insert stack protectors
 ; CHECK-NEXT:       Module Verifier
+; CHECK-NEXT:       Assignment Tracking Analysis
 ; CHECK-NEXT:       X86 DAG->DAG Instruction Selection
 ; CHECK-NEXT:       X86 PIC Global Base Reg Initialization
 ; CHECK-NEXT:       Finalize ISel and expand pseudo-instructions

llvm/test/CodeGen/X86/opt-pipeline.ll

@@ -80,6 +80,7 @@
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:       Post-Dominator Tree Construction
 ; CHECK-NEXT:       Branch Probability Analysis
+; CHECK-NEXT:       Assignment Tracking Analysis
 ; CHECK-NEXT:       Lazy Branch Probability Analysis
 ; CHECK-NEXT:       Lazy Block Frequency Analysis
 ; CHECK-NEXT:       X86 DAG->DAG Instruction Selection