revert part of "small optimisations"

from
    commit ad1e790d76492ca4465114ad17e32912242db34f
    Date:   Fri Jul 5 14:12:24 2019 +0200
    small optimisations
I had in mind that resize() always changes capacity to the specified
value, but it actually follows the normal capacity expansion strategy
for vector

Change-Id: Idf677825d0f1f95b87110a3789ba95356d3771aa
Reviewed-on: https://gerrit.libreoffice.org/75193
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
diff --git a/comphelper/source/streaming/memorystream.cxx b/comphelper/source/streaming/memorystream.cxx
index 4477cd0..741c434 100644
--- a/comphelper/source/streaming/memorystream.cxx
+++ b/comphelper/source/streaming/memorystream.cxx
@@ -197,7 +197,7 @@ void SAL_CALL UNOMemoryStream::writeBytes( const Sequence< sal_Int8 >& aData )
        }

        if( static_cast< sal_Int32 >( nNewSize ) > static_cast< sal_Int32 >( maData.size() ) )
            maData.insert( maData.end(), nNewSize - maData.size(), 0 );
            maData.resize( nNewSize );

        sal_Int8* pData = &(*maData.begin());
        sal_Int8* pCursor = &(pData[mnCursor]);