docs: umask argument is not optional
Fixes
ext/posix/sys/stat.c (umask): Document arguments correctly.
@@ -304,7 +304,7 @@ Pstat(lua_State *L)
/***
Set file mode creation mask.
@function umask
-@int[opt] mode new file creation mask
+@int mode new file creation mask
@treturn int previous umask
@see umask(2)
@see posix.umask
