Werk #12781: Update monitoring-plugins from 2.3 to 2.3.1

Component	Checks & agents
Title	Update monitoring-plugins from 2.3 to 2.3.1
Date	Apr 22, 2021
Level	Trivial Change
Class	New Feature
Compatibility	Compatible - no manual interaction needed
Checkmk versions & editions	2.1.0b1 Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk MSP (CME)

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