[libc++][NFC] Fix typo in comment

NOKEYCHECK=True
GitOrigin-RevId: dd662f0f3d6c400ca3cf1feeedd5102985626a18
diff --git a/src/locale.cpp b/src/locale.cpp
index f1978e0..c1b9726 100644
--- a/src/locale.cpp
+++ b/src/locale.cpp
@@ -4380,7 +4380,7 @@
     dest = res;
     return true;
   }
-  // FIXME: Work around specific multibyte sequences that we can reasonable
+  // FIXME: Work around specific multibyte sequences that we can reasonably
   // translate into a different single byte.
   switch (wout) {
   case L'\u202F': // narrow non-breaking space