man: Remove BUGS sections containing obvious or misplaced information

The BUGS section in u-a(8) just contains obvious instructions. The one
in deb-substvars(5) comes from dpkg-source(1), and got wrongly carried
over during the big dpkg-source(1) man page split.

debian/changelog

@@ -12,6 +12,7 @@ dpkg (1.17.0) UNRELEASED; urgency=low
     - Remove unneeded double quotes in .SH headings.
     - Do not use “header” when “format” or “field” is meant.
     - Move dangers of installing via dpkg-deb from BUGS to a NOTES section.
+    - Remove BUGS sections containing obvious or misplaced information.
   * Use colon instead of dot for user:group in dpkg debug output.
   * Remove support for obsolete DM-Upload-Allowed from Dpkg::Vendor::Debian.
   * Fix update-alternatives to use the current alternative link as the first

man/deb-substvars.5

@@ -165,10 +165,6 @@ and an empty value is assumed.
 .B debian/substvars
 List of substitution variables and values.
 .
-.SH BUGS
-The point at which field overriding occurs compared to certain
-standard output field settings is rather confused.
-
 .SH SEE ALSO
 .ad l
 .nh

man/update-alternatives.8

@@ -510,14 +510,6 @@ this as root:
 .B update\-alternatives \-\-auto vi
 .RE
 .
-.SH BUGS
-If you find a bug, please report it using the Debian bug-tracking system.
-.PP
-If you find any discrepancy between the operation of
-.B update\-alternatives
-and this manual page, it is a bug,
-either in the implementation or the documentation; please report it.
-.
 .SH SEE ALSO
 .BR ln (1),
 FHS, the Filesystem Hierarchy Standard.