add missed separator

Author: caic99

doc/env.md

@@ -88,6 +88,7 @@ These environment variables also apply to third-party programs using the C++ int
 **Type**: List of paths, split by `:` on Unix and `;` on Windows
 
 List of customized OP plugin libraries to load, such as `/path/to/plugin1.so:/path/to/plugin2.so` on Linux and `/path/to/plugin1.dll;/path/to/plugin2.dll` on Windows.
+:::
 
 :::{envvar} DP_PROFILER
 
@@ -118,4 +119,4 @@ Tips:
 
 - Large runs can generate sizable JSON files; consider limiting numbers of MD steps, like 20.
 - Currently this feature only supports single process, or multi-process runs where each process uses a distinct GPU on the same node.
-  :::
+:::