Fix some typos (GH-14435)

diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index a75a3c9..552cb78 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -1552,7 +1552,7 @@
 
     (a - 1)**2 < (n >> 2*(c - d)) < (a + 1)**2
 
-To faciliate the proof, we make some changes of notation. Write `m` for
+To facilitate the proof, we make some changes of notation. Write `m` for
 `n >> 2*(c-d)`, and write `b` for the new value of `a`, so
 
     b = (a << d - e - 1) + (n >> 2*c - e - d + 1) // a