Fix off-by-one error in DeflatePlugin.

Thanks to @fmateoc for pointing this out!
See http://lists.squeakfoundation.org/pipermail/vm-dev/2022-January/037536.html

src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/nodes/plugins/Zip.java

@@ -579,12 +579,12 @@ public long primitiveZipSendBlock(final PointersObject rcvr, final PointersObjec
         zipPosition = fetchIntegerofObject(1, rcvr);
         /* zipWriteLimit := interpreterProxy fetchInteger: 3 ofObject: rcvr. */
         zipReadLimit = fetchIntegerofObject(2, rcvr);
-        zipBitBuf = fetchIntegerofObject(writeStreamInstSize + 1, rcvr);
-        zipBitPos = fetchIntegerofObject(writeStreamInstSize + 2, rcvr);
+        zipBitBuf = fetchIntegerofObject(writeStreamInstSize + 0, rcvr);
+        zipBitPos = fetchIntegerofObject(writeStreamInstSize + 1, rcvr);
         final long result = sendBlockwithwithwith(litStream, distStream, litTree, distTree);
         storeIntegerofObjectwithValue(1, rcvr, zipPosition);
-        storeIntegerofObjectwithValue(readStreamInstSize + 1, rcvr, zipBitBuf);
-        storeIntegerofObjectwithValue(readStreamInstSize + 2, rcvr, zipBitPos);
+        storeIntegerofObjectwithValue(writeStreamInstSize + 0, rcvr, zipBitBuf);
+        storeIntegerofObjectwithValue(writeStreamInstSize + 1, rcvr, zipBitPos);
         return result;
     }