site: exchange CI signing key for nightly and experimental

Exchange the signing key used by the CI/CD pipeline with a new key.

site.conf

@@ -193,7 +193,7 @@
                     'b7077095e9d3fc892db1c280b78b65d737700c9aea70a6998d6aad8b3146aaed', -- flip
                     '8cede21f8275b20add6cdff85fa1fbd710e0e4ccbd94faed43854a0533207a60', -- nrb
                     '6177c49629d26197f916c77fa7d7ba902500f20d6e4b02c621e3696d1ef10232', -- 0x4A6F
-                    '846d469d5a65cf23dcb4656a33c0e658cf14de40f60ec120a0aed012b011821c', -- gitlab runner
+                    '4d4417f25702ca1dded74dde7510dab5c13fde3a105bb704bd2d2d250ece0109', -- gitlab runner 20200605
                 },
             },
             experimental = {
@@ -208,7 +208,7 @@
                     'b7077095e9d3fc892db1c280b78b65d737700c9aea70a6998d6aad8b3146aaed', -- flip
                     '8cede21f8275b20add6cdff85fa1fbd710e0e4ccbd94faed43854a0533207a60', -- nrb
                     '6177c49629d26197f916c77fa7d7ba902500f20d6e4b02c621e3696d1ef10232', -- 0x4A6F
-                    '846d469d5a65cf23dcb4656a33c0e658cf14de40f60ec120a0aed012b011821c', -- gitlab runner
+                    '4d4417f25702ca1dded74dde7510dab5c13fde3a105bb704bd2d2d250ece0109', -- gitlab runner 20200605
                 },
             },
         },