Update comment with new 'in' operator.

Bug: 31997910
Test: Compile.
Change-Id: I453e288ad0ef6a1d241b55ca73adbc3dfb17b65a
diff --git a/syscall_filter.c b/syscall_filter.c
index 34f6b3a..5262af3 100644
--- a/syscall_filter.c
+++ b/syscall_filter.c
@@ -265,7 +265,7 @@
 	 * Atoms are of the form "arg{DNUM} {OP} {NUM}"
 	 * where:
 	 *   - DNUM is a decimal number.
-	 *   - OP is an operator: ==, !=, or & (flags set).
+	 *   - OP is an operator: ==, !=, & (flags set), or 'in' (inclusion).
 	 *   - NUM is an octal, decimal, or hexadecimal number.
 	 *
 	 * When the syscall arguments make the expression true,