Fix doc for data invariant & remove tuple header

Author: Sonny Martin

src/util/invariant.h

@@ -12,7 +12,6 @@ Author: Martin Brain, martin.brain@diffblue.com
 #include <cstdlib>
 #include <stdexcept>
 #include <string>
-#include <tuple>
 #include <type_traits>
 
 /*
@@ -376,7 +375,7 @@ invariant_violated_string(
 
 // This condition should be used to document that assumptions that are
 // made on goto_functions, goto_programs, exprts, etc. being well formed.
-// "The data structure is corrupt or malformed"
+// "The data structure is not corrupt or malformed"
 #define DATA_INVARIANT2(CONDITION, REASON) INVARIANT2(CONDITION, REASON)
 #define DATA_INVARIANT3(CONDITION, REASON, DIAGNOSTICS)                        \
   INVARIANT3(CONDITION, REASON, DIAGNOSTICS)