doc: fix casing in stream.md

PR-URL: #23166
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Vse Mozhet Byt <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>

Author: Sintendo

doc/api/stream.md

@@ -1307,7 +1307,7 @@ added: v8.0.0
 
 Destroy the stream, and emit `'error'`. After this call, the
 transform stream would release any internal resources.
-implementors should not override this method, but instead implement
+Implementors should not override this method, but instead implement
 [`readable._destroy()`][readable-_destroy].
 The default implementation of `_destroy()` for `Transform` also emit `'close'`.