Revert "add assert to check integer overflow for table size (#1402)" (#…

…1406)

This reverts commit 7f4e4b5. 
This revert is necessary because b.sz won't exist after builder changes are
reverted and the assert is no longer valid.

The commit 7f4e4b5 is being reverted because we have seen some crashes
which could be caused by these changes. We haven't been able to reproduce the
crashes yet.

Related to #1389, #1388, #1387
Also see https://discuss.dgraph.io/t/current-state-of-badger-crashes/7602

table/builder.go

@@ -327,9 +327,6 @@ func (b *Builder) shouldFinishBlock(key []byte, value y.ValueStruct) bool {
 		// So, size of IV is added to estimatedSize.
 		estimatedSize += aes.BlockSize
 	}
-	// Integer overflow check for table size.
-	y.AssertTrue(uint64(b.sz)+uint64(estimatedSize) < math.MaxUint32)
-
 	return estimatedSize > uint32(b.opt.BlockSize)
 }