prepare release 4.0.6

RELEASE-NOTES

@@ -1,3 +1,9 @@
+# Release 4.0.6 - (Dec 4, 2020)
+ * Fix 'Max' button issue for submarine swaps button (#6770)
+ * Fix 'Max' button in kivy (#6169)
+ * Various fixes for Kivy/Android install wizard
+ * More robust account keypath for BitBox02 (#6766)
+
 # Release 4.0.5 - (Nov 18, 2020)
  * Fix .dmg binary hanging on recently released macOS 11 Big Sur (#6461)
  * Lightning:

electrum/version.py

@@ -1,5 +1,5 @@
-ELECTRUM_VERSION = '4.0.5'     # version of the client package
-APK_VERSION = '4.0.5.0'        # read by buildozer.spec
+ELECTRUM_VERSION = '4.0.6'     # version of the client package
+APK_VERSION = '4.0.6.0'        # read by buildozer.spec
 
 PROTOCOL_VERSION = '1.4'     # protocol version requested