docs/man/victronups.txt: update link to cable pinout

Closes: #1371

Author: jimklimov

docs/man/victronups.txt

@@ -28,7 +28,8 @@ CABLING
 If your Victron cable is broken or missing, use this diagram to build
 a clone:
 
-docs/cables/victron.txt
+* https://github.com/networkupstools/nut/blob/master/docs/cables/ge-imv-victron.txt
+* link:docs/cables/ge-imv-victron.txt[]
 
 EXTRA ARGUMENTS
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