docs: Prepare version 0.4.2 release notes

Change-Id: I36780f66b803b6049e5399fde6e1a097c40a65b3
diff --git a/docs/release-notes/release-notes-0.4.2.rst b/docs/release-notes/release-notes-0.4.2.rst
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+NLSR version 0.4.2
+++++++++++++++++++
+
+**Bug Fixes**:
+
+- Fix segfault in scheduled erase of lsa segment (:issue:`4520`)