Temp fix for slow onEnter issue

The issue was windows specific -- cancellation caused collection of
bracktraces at some point, and that was slow on windows.

The proper fix here is to make sure that we don't collect bracktraces
unnecessary (which we currently do due to failure), but, as a
temporary fix, let's just not force their collection in the first
place!

crates/ra_lsp_server/src/main.rs

@@ -6,7 +6,8 @@
 use ra_prof;
 
 fn main() -> Result<()> {
-    std::env::set_var("RUST_BACKTRACE", "short");
+    // re-enable and verify on windows after #1400
+    // std::env::set_var("RUST_BACKTRACE", "short");
     let logger = Logger::with_env_or_str("error").duplicate_to_stderr(Duplicate::All);
     match std::env::var("RA_LOG_DIR") {
         Ok(ref v) if v == "1" => logger.log_to_file().directory("log").start()?,