patch 8.2.3914: various spelling mistakes in comments

Problem:    Various spelling mistakes in comments.
Solution:   Fix the mistakes. (Dominique Pellé, closes #9416)
diff --git a/src/os_unix.c b/src/os_unix.c
index 1c00f22..77f35db 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -3165,7 +3165,7 @@
     // Therefore, this check does not have any sense - let keep us to the
     // conventions instead:
     // *.COM and *.EXE files are the executables - the rest are not. This is
-    // not ideal but better then it was.
+    // not ideal but better than it was.
     int vms_executable = 0;
     if (S_ISREG(st.st_mode) && mch_access((char *)name, X_OK) == 0)
     {