Improve wording

Co-authored-by: LeSeulArtichaut <leseulartichaut@gmail.com>

src/building/bootstrapping.md

@@ -184,7 +184,7 @@ Note that there are two `std` libraries in play here:
 2. The library _used to compile programs_ with `stageN/rustc`, which was
    built by stage N (stage N `std`).
 
-stage N `std` is pretty much necessary for any useful work with the stage N compiler.
+Stage N `std` is pretty much necessary for any useful work with the stage N compiler.
 Without it, you can only compile programs with `#![no_core]` -- not terribly useful!
 
 The reason these need to be different is because they aren't necessarily ABI-compatible:
@@ -194,7 +194,7 @@ to Rust metadata on nightly that aren't present in beta.
 This is also where `--keep-stage 1 library/std` comes into play. Since most
 changes to the compiler don't actually change the ABI, once you've produced a
 `std` in stage 1, you can probably just reuse it with a different compiler.
-If the ABI hasn't changed, you're good to go, no need to spend the time
+If the ABI hasn't changed, you're good to go, no need to spend time
 recompiling that `std`.
 `--keep-stage` simply assumes the previous compile is fine and copies those
 artifacts into the appropriate place, skipping the cargo invocation.