Work around Doxygen 1.9.7 change

Doxygen 1.9.7 avoids duplicating member definitions in the XML
documents for groups and header files (doxygen/doxygen#9797).  This
change breaks the current Doxygen-REST bridge, which expects to find
memberdef elements in krb5_8hin.xml.  To work around this problem,
remove the @group and @ref declarations in krb5.hin; they were not
translated into REST as it was.

Also remove a deprecated setting in Doxyfile.

(cherry picked from commit 6ed1f8e27eb624710c4aa152d8dee4cf2e528082)

https://github.com/krb5/krb5/commit/59941e53776acc1e718faeb5409d39e8165957ba
Author: Greg Hudson <ghudson@mit.edu>
Commit: 59941e53776acc1e718faeb5409d39e8165957ba
Branch: krb5-1.21
 src/doc/Doxyfile.in       |  1 -
 src/include/krb5/krb5.hin | 93 ++++++++++++++++-------------------------------
 2 files changed, 32 insertions(+), 62 deletions(-)