Update source/uax31.tex

Co-authored-by: Johel Ernesto Guerrero Peña <[email protected]>

Author: jensmaurer

source/uax31.tex

@@ -55,7 +55,7 @@
 \pnum
 \Cpp{} does not allow format characters in identifiers, so this does not apply.
 
-\rSec1[uaxid.stable]{R1b Stable identifiers}
+\rSec2[uaxid.stable]{R1b Stable identifiers}
 
 \pnum
 An implementation of UAX \#31 may choose to guarantee