Merge pull request #2767 from rust-lang/tshepang-patch-1

typo

Author: tshepang

src/building/bootstrapping/what-bootstrapping-does.md

@@ -243,7 +243,7 @@ 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 `stage1`, 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 time recompiling
-that `std`. The flag `--keep-stage` simply instructs the build script to assumes
+that `std`. The flag `--keep-stage` simply instructs the build script to assume
 the previous compile is fine and copies those artifacts into the appropriate
 place, skipping the `cargo` invocation.