Remove unnecessary check - fixed in std since Rust 1.38

issue now closed: rust-lang/rust#63326
fix landed in a rollup: rust-lang/rust#63380 merged aug 8, 2019
rust 1.38 beta cut on aug 15, 2019: https://blog.rust-lang.org/2019/08/15/Rust-1.37.0.html
minimum supported rust version for this repo is currently 1.41.

Author: pchickey

crates/wasi-common/src/snapshots/wasi_snapshot_preview1.rs

@@ -172,10 +172,6 @@ impl<'a> WasiSnapshotPreview1 for WasiCtx {
     fn fd_filestat_set_size(&self, fd: types::Fd, size: types::Filesize) -> Result<()> {
         let required_rights = HandleRights::from_base(types::Rights::FD_FILESTAT_SET_SIZE);
         let entry = self.get_entry(fd)?;
-        // This check will be unnecessary when rust-lang/rust#63326 is fixed
-        if size > i64::max_value() as u64 {
-            return Err(Errno::TooBig);
-        }
         entry.as_handle(&required_rights)?.filestat_set_size(size)
     }