cmd/k8s-operator: rename 'l' variables (#17700)

Single letter 'l' variables can eventually become confusing when
they're rendered in some fonts that make them similar to 1 or I.

Updates #cleanup

Signed-off-by: Fernando Serboncini <fserb@tailscale.com>

cmd/k8s-operator/proxygroup.go

@@ -80,7 +80,7 @@ var (
 // ProxyGroupReconciler ensures cluster resources for a ProxyGroup definition.
 type ProxyGroupReconciler struct {
 	client.Client
-	l        *zap.SugaredLogger
+	log      *zap.SugaredLogger
 	recorder record.EventRecorder
 	clock    tstime.Clock
 	tsClient tsClient
@@ -101,7 +101,7 @@ type ProxyGroupReconciler struct {
 }
 
 func (r *ProxyGroupReconciler) logger(name string) *zap.SugaredLogger {
-	return r.l.With("ProxyGroup", name)
+	return r.log.With("ProxyGroup", name)
 }
 
 func (r *ProxyGroupReconciler) Reconcile(ctx context.Context, req reconcile.Request) (_ reconcile.Result, err error) {