update VectorValues::== docstring

gtsam/linear/VectorValues.h

@@ -263,7 +263,7 @@ namespace gtsam {
     /** equals required by Testable for unit testing */
     bool equals(const VectorValues& x, double tol = 1e-9) const;
 
-    /// Check exact equality.
+    /// Check equality.
     friend bool operator==(const VectorValues& lhs, const VectorValues& rhs) {
       return lhs.equals(rhs);
     }