Rollup merge of rust-lang#126030 - ChrisDenton:update-wingen-readme, …

…r=Mark-Simulacrum

Update `./x fmt` command in library/std/src/sys/pal/windows/c/README.md

`./x fmt` no longer accepts paths so the command in the readme won't work.

library/std/src/sys/pal/windows/c/README.md

@@ -3,7 +3,7 @@ be edited manually.
 
 To add bindings, edit `bindings.txt` then regenerate using the following command:
 
-    ./x run generate-windows-sys && ./x fmt library/std
+    ./x run generate-windows-sys && ./x fmt
 
 If you need to override generated functions or types then add them to
 `library/std/src/sys/pal/windows/c.rs`.