[depr.format.syn] Fix header reference

tkoeppe · tkoeppe · commit e9604bcd3d83 · 2024-10-16T21:12:40.000+01:00
diff --git a/source/future.tex b/source/future.tex
@@ -679,7 +679,7 @@
 \rSec2[depr.format.syn]{Header \tcode{<format>} synopsis}
 
 \pnum
-The header \libheaderref{format}{format.syn} has the following additions:
+The header \libheaderref{format} has the following additions:
 
 \begin{codeblock}
 namespace std {
