Update number of subsections in Value Conversions

Author: fthomas

spec/06-expressions.md

@@ -1341,7 +1341,7 @@ to $U$ after applying [eta-expansion](#eta-expansion) and
 
 ### Value Conversions
 
-The following five implicit conversions can be applied to an
+The following seven implicit conversions can be applied to an
 expression $e$ which has some value type $T$ and which is type-checked with
 some expected type $\mathit{pt}$.