[BOLT] Fix pseudo calculation in BinaryBasicBlock

Summary:
A recent commit broke our tests because it was depending on
getNumNonPseudos() at a very late stage of our optimization pipeline.
The problem was in a instruction deletion member function in
BinaryBasicBlock that was not updating the number of pseudos after
deletion. Fix this.

(cherry picked from FBD9305972)

bolt/src/BinaryBasicBlock.h

@@ -669,6 +669,7 @@ public:
 
   /// Erase non-pseudo instruction at a given iterator \p II.
   iterator eraseInstruction(iterator II) {
+    adjustNumPseudos(*II, -1);
     return Instructions.erase(II);
   }