Bump bootstrap to released stable

Author: Mark-Simulacrum

src/stage0.txt

@@ -12,7 +12,7 @@
 # source tarball for a stable release you'll likely see `1.x.0` for rustc and
 # `0.(x+1).0` for Cargo where they were released on `date`.
 
-date: 2020-06-01
+date: 2020-06-04
 rustc: 1.44.0
 cargo: 0.45.0
 
@@ -40,4 +40,4 @@ cargo: 0.45.0
 # looking at a beta source tarball and it's uncommented we'll shortly comment it
 # out.
 
-dev: 1
+#dev: 1