package/libkrb5: security bump to version 1.21.3

For the change log, see [1].

The license hash file changed, due to the year update.  See [2].  This
commit also adds a comment in the hash file about the pgp signature file
source and key id used for the verification.

Fixes:
- https://nvd.nist.gov/vuln/detail/CVE-2024-37370
- https://nvd.nist.gov/vuln/detail/CVE-2024-37371

[1] https://web.mit.edu/kerberos/www/krb5-1.21/
[2] https://github.com/krb5/krb5/commit/fec2c44ee93bfd3282bed99509a941d56a6e2c21

Signed-off-by: Julien Olivain <ju.o@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 0416ae0ed5853cd7da4b34e9f8cd17baabf503f0)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libkrb5/libkrb5.hash

@@ -1,5 +1,7 @@
 # Locally calculated after checking pgp signature
-sha256  9560941a9d843c0243a71b17a7ac6fe31c7cebb5bce3983db79e52ae7e850491  krb5-1.21.2.tar.gz
+# from https://web.mit.edu/kerberos/dist/krb5/1.21/krb5-1.21.3.tar.gz.asc
+# with key C4493CB739F4A89F9852CBC20CBA08575F8372DF
+sha256  b7a4cd5ead67fb08b980b21abd150ff7217e85ea320c9ed0c6dadd304840ad35  krb5-1.21.3.tar.gz
 
 # Hash for license file:
-sha256  0d5373486138cb176c063db98274b4c4ab6ef3518c4191360736384b780306c2  NOTICE
+sha256  7601361a275aadbe35c90185519323c28730d60c553683e56fd06cf9c5f749a6  NOTICE

package/libkrb5/libkrb5.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 LIBKRB5_VERSION_MAJOR = 1.21
-LIBKRB5_VERSION = $(LIBKRB5_VERSION_MAJOR).2
+LIBKRB5_VERSION = $(LIBKRB5_VERSION_MAJOR).3
 LIBKRB5_SITE = https://web.mit.edu/kerberos/dist/krb5/$(LIBKRB5_VERSION_MAJOR)
 LIBKRB5_SOURCE = krb5-$(LIBKRB5_VERSION).tar.gz
 LIBKRB5_SUBDIR = src