mark rustfmt as broken

There's a trailing whitespace problem in one of the tests. @nrc said
he'll go fix it quickly, but until then I'll like to land this PR.

I suspect this happened because one of the dependencies in the
Cargo.lock I updated had changed the format of the XML they emit, but
that has to be investigated.

Author: arielb1

src/tools/toolstate.toml

@@ -32,4 +32,4 @@ clippy = "Broken"
 rls = "Testing"
 
 # ping @nrc
-rustfmt = "Testing"
+rustfmt = "Compiling"