helm: fix extraArgs trailing backslash issue

Remove trailing backslash after the last extraArgs argument to avoid
shell syntax error. Use counter to only add backslash between arguments.

k8s/charts/seaweedfs/templates/all-in-one/all-in-one-deployment.yaml

@@ -297,8 +297,9 @@ spec:
               -sftp.userStoreFile=/etc/sw/sftp/seaweedfs_sftp_config \
               {{- end }}
               {{- end }}
-              {{- range .Values.allInOne.extraArgs }}
-              {{ . }} \
+              {{- $extraArgsCount := len .Values.allInOne.extraArgs }}
+              {{- range $i, $arg := .Values.allInOne.extraArgs }}
+              {{ $arg }}{{ if ne (add1 $i) $extraArgsCount }} \{{ end }}
               {{- end }}
 
           volumeMounts: