Remove backup file reference from cargo checksum

[vparfonov]

This PR removes the reference to autoconf.h.in~ from vendor/krb5-src/.cargo-checksum.json.
During vendoring of krb5-src, a backup file named autoconf.h.in~ was included in the generated vendor/krb5-src/.cargo-checksum.json.
This file is not required for the build (it’s an editor-generated backup, likely from autoconf.h.in)

No functional changes to code or dependency versions.

/cc @Clee2691 @cahartma
/assign @jcantrill

[openshift-ci]

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