"\n" not supported anymore by Mermaid for newline

Current behavior "\n" does not work anymore on Mermaid live.

%%{init: {'flowchart': { 'curve': 'monotoneY'}, 'fontFamily': 'Verdana' } }%%
flowchart TB

ReLU_0("relu_0<br/><sub><em>(ReLU#0)</em></sub>"):::rootCls
input0((in#0)):::inputCls--->|"&rarr;0"|ReLU_0
ReLU_0--->|"0&rarr;"|output0((out#0)):::outputCls
classDef inputCls fill:#afa
classDef outputCls fill:#ffa
classDef externalCls fill:#ccc
classDef producerCls fill:#ccf
classDef genericCls fill:#f9f9ff,stroke-width:1px,stroke-dasharray: 5 5
classDef metaCls stroke-width:5px
classDef rootCls stroke:#f00
classDef producerCls_rootCls stroke:#f00,fill:#ccf
classDef genericCls_rootCls stroke:#f00,fill:#f9f9ff,stroke-width:1px,stroke-dasharray: 5 5
classDef metaCls_rootCls stroke:#f00,stroke-width:5px

We should use
instead as suggested on the Mermaid documentation. (not
because there could be a warning of none closing tag)