Update `sebastinez` signing key — radicle.xyz

Due to moving from a VPS build server to my local setup, I’m signing the new builds with my local identity.

 <table>
   <thead><th>Signer</th></thead>
   <tr><td>Key</td><td><code>ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKU7IHRsae2q1/qd8NaWxfGhPEFGHwK1dcxvSjNdttjb</code></td></tr>
   <tr><td>Fingerprint</td><td><code>SHA256:mqjWN1YrPRDTcVTxB4IZPHyH+vXpjWSogi+3zezZ/rQ</code></td></tr>
   <tr><td>Key</td><td><code>ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIFw+wCPZUh8OndhgavJMSZluorVvzJjz22PH81XrkvIu</code></td></tr>
   <tr><td>Fingerprint</td><td><code>SHA256:HYV32eX6vSKEXpuXNstYGsbWDYTOxG1eqv/HjwuZnck</code></td></tr>
   <tr><td>Owner</td><td>me@sebastinez.dev</td></tr>
 </table>