Fix a comment typo

Author: atrick

lib/SIL/Utils/OSSALifetimeCompletion.cpp

@@ -31,8 +31,8 @@
 ///     end_borrow %phi1
 ///     %k1 = destroy_value %v1 // must be below end_borrow %phi1
 ///
-/// When completing the lifetime for a (%phi2) transitively include all inner
-/// adjacent reborrows (%phi1):
+/// When completing the lifetime for a phi (%phi2) transitively include all
+/// inner adjacent reborrows (%phi1):
 ///
 ///   bb1:
 ///     %v1 = ...