Move the i to the right place in the help string (#452)

(Really, fix two typos)
diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 912ce4e..683b6d2 100644
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -1724,7 +1724,7 @@
         help="Use an existing repository instead of cloning from github",
     )
     runner.add_argument(
-        "--use_bazel_at_commit", type=str, help="Use Bazel binariy built at a specifc commit"
+        "--use_bazel_at_commit", type=str, help="Use Bazel binary built at a specific commit"
     )
     runner.add_argument("--use_but", type=bool, nargs="?", const=True)
     runner.add_argument("--save_but", type=bool, nargs="?", const=True)