man: Fix typo in dpkg-buildflags(1)

man/dpkg-buildflags.1

@@ -43,7 +43,7 @@ temporarily by the user with environment variables (see section
 dynamically by the package maintainer with environment variables set via
 \fBdebian/rules\fP (see section \fBENVIRONMENT\fP).
 .P
-The configuration files can contain two types of directives:
+The configuration files can contain four types of directives:
 .TP
 .BI SET " flag value"
 Override the flag named \fIflag\fP to have the value \fIvalue\fP.