example: match duration unmarshal

as described in #95,
given that the unmarshalling that source-controller performs doesn't
match what we're trying to submit, we end up forcing reconciliation to
happen over and over again (better described in the issue).

now that we make use of informers rather than a 5s polling interval, the
issue becomes even more apparent.

ultimately we should figure out #95, but for now, this fix prevents a
big unecessary reconciliation load.

Signed-off-by: Ciro S. Costa <ciroscosta@vmware.com>

examples/source-to-knative-service/app-operator/supply-chain-templates.yaml

@@ -36,7 +36,7 @@ spec:
     metadata:
       name: $(workload.metadata.name)$
     spec:
-      interval: 1m
+      interval: 1m0s
       url: $(workload.spec.source.git.url)$
       ref: $(workload.spec.source.git.ref)$
       gitImplementation: libgit2