revisionstore: fix default pending data pack limit

Summary:
The old code tried to express 4GB by using ^ to do an exponent. That
operator is actually the bitwise xor, so this was producing a limit closer to 4
bytes. It doesn't seem to have mattered much since a later diff overrode the
default via dynamicconfig. But let's fix this anyway.

Reviewed By: krallin

Differential Revision: D23955629

fbshipit-source-id: 6abebcb7e84b7a47f70ac501fa11b0dc60dfda7b

eden/scm/lib/revisionstore/src/contentstore.rs

@@ -275,7 +275,7 @@ impl<'a> ContentStoreBuilder<'a> {
             .config
             .get_or("packs", "maxdatapendingbytes", || {
                 // Default to 4GB
-                ByteCount::from(4 * (1024 ^ 3))
+                ByteCount::from(4 * (1024 * 1024 * 1024))
             })?
             .value();
         let max_bytes = self