v15.1.0.md: fix wrong syntax highlighting (#3695)

Author: XhmikosR

locale/en/blog/release/v15.1.0.md

@@ -104,7 +104,7 @@ When generating snapshots, garbage collection may be triggered and bring the hea
 
 Generating V8 snapshots takes time and memory (both memory managed by the V8 heap and native memory outside the V8 heap). The bigger the heap is, the more resources it needs. Node.js will adjust the V8 heap to accommondate the additional V8 heap memory overhead, and try its best to avoid using up all the memory avialable to the process.
 
-```console
+```shell-session
 $ node --max-old-space-size=100 --heapsnapshot-near-heap-limit=3 index.js
 Wrote snapshot to Heap.20200430.100036.49580.0.001.heapsnapshot
 Wrote snapshot to Heap.20200430.100037.49580.0.002.heapsnapshot