[dataflow] Remove [[deprecated]] from deprecated functions

This fixes -Werror -Wdeprecated builds
See D153469

Author: sam-mccall

clang/include/clang/Analysis/FlowSensitive/DataflowEnvironment.h

@@ -529,13 +529,13 @@ class Environment {
 
   /// Adds `Val` to the set of clauses that constitute the flow condition.
   void addToFlowCondition(const Formula &);
-  LLVM_DEPRECATED("Use Formula version instead", "")
+  /// Deprecated: Use Formula version instead.
   void addToFlowCondition(BoolValue &Val);
 
   /// Returns true if and only if the clauses that constitute the flow condition
   /// imply that `Val` is true.
   bool flowConditionImplies(const Formula &) const;
-  LLVM_DEPRECATED("Use Formula version instead", "")
+  /// Deprecated: Use Formula version instead.
   bool flowConditionImplies(BoolValue &Val) const;
 
   /// Returns the `DeclContext` of the block being analysed, if any. Otherwise,