[2097] unrelated trivial fixes to doxygen comments.

src/lib/datasrc/memory/domaintree.h

@@ -930,7 +930,7 @@ private:
     /// \brief The destructor.
     ///
     /// An object of this class is always expected to be destroyed explicitly
-    /// by \c destroy(), so the constructor is hidden as private.
+    /// by \c destroy(), so the destructor is hidden as private.
     ///
     /// \note DomainTree is not intended to be inherited so the destructor
     /// is not virtual

src/lib/datasrc/memory/rdata_encoder.h

@@ -100,8 +100,7 @@ namespace memory {
 /// \brief General error in RDATA encoding.
 ///
 /// This is thrown when \c RdataEncoder encounters a rare, unsupported
-/// situation. a method is called for a name or RRset which
-/// is not in or below the zone.
+/// situation.
 class RdataEncodingError : public Exception {
 public:
     RdataEncodingError(const char* file, size_t line, const char* what) :