Add changelog for 4.2.1-1 release

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>

debian/changelog

+python-openqa-client (4.2.1-1) unstable; urgency=medium
+
+  * New upstream version 4.2.1
+  * Add watch file.
+  * Update Standards-Version to 4.6.1.0
+
+ -- Sudip Mukherjee <sudipm.mukherjee@gmail.com>  Sat, 12 Nov 2022 21:41:07 +0000
+
 python-openqa-client (4.1.2-2) unstable; urgency=medium
 
   * Source only upload.