Use 1.43.1 release

Author: Mark-Simulacrum

src/stage0.txt

@@ -12,8 +12,8 @@
 # source tarball for a stable release you'll likely see `1.x.0` for rustc and
 # `0.x.0` for Cargo where they were released on `date`.
 
-date: 2020-04-21
-rustc: 1.43.0
+date: 2020-05-07
+rustc: 1.43.1
 cargo: 0.44.0
 
 # We use a nightly rustfmt to format the source because it solves some
@@ -40,4 +40,4 @@ cargo: 0.44.0
 # looking at a beta source tarball and it's uncommented we'll shortly comment it
 # out.
 
-dev: 1
+#dev: 1