[doc] Improve documentation of (pre|post)run_cmds

reframe/core/pipeline.py

@@ -401,7 +401,7 @@ def pipeline_hooks(cls):
 
     #: .. versionadded:: 3.0
     #:
-    #: List of shell commands to execute before launching this job.
+    #: List of shell commands to execute before the parallel launch command.
     #:
     #: These commands do not execute in the context of ReFrame.
     #: Instead, they are emitted in the generated job script just before the
@@ -413,7 +413,7 @@ def pipeline_hooks(cls):
 
     #: .. versionadded:: 3.0
     #:
-    #: List of shell commands to execute after launching this job.
+    #: List of shell commands to execute after the parallel launch command.
     #:
     #: See :attr:`prerun_cmds` for a more detailed description of the
     #: semantics.