BUG/MEDIUM: htx: Don't count delta twice when block value is replaced

A regression was introduced by the commit a8887e55a ("BUG/MEDIUM: htx: Fix
function used to change part of a block value when defrag").

When a block value was replaced and a defragmentation was performed, the
delta between the old value and the new one was counted twice. htx_defrag()
already is responsible to set the new size for the HTX message. So it must
not be performed in htx_replace_blk_value().

This patch must be backported with the commit above. So theorically to all
stable versions.

src/htx.c

@@ -718,8 +718,6 @@ struct htx_blk *htx_replace_blk_value(struct htx *htx, struct htx_blk *blk,
 		/* finally copy data */
 		htx_memcpy(htx_get_blk_ptr(htx, blk), b_orig(chunk), b_data(chunk));
 		free_trash_chunk(chunk);
-
-		htx->data += delta;
 	}
 	return blk;
 }