[BZip2] Additionally reduce block sizes by 1.25

This is required, because, apparently, original bzip2 implementation doesn't account for the fact that the initial RLE can cause expansion of the data.

Sources/BZip2/BZip2+BlockSize.swift

@@ -60,7 +60,7 @@ public extension BZip2 {
         }
 
         var sizeInBytes: Int {
-            return self.rawValue * 100 * 1000
+            return self.rawValue * 100 * 800
         }
 
     }