fix(deps): update prom/alertmanager docker tag to v0.31.1

Author: renovate[bot]

Dockerfile

@@ -2,7 +2,7 @@
 #FROM codercom/code-server:3.11.1 as code-server 
 FROM codercom/code-server:3.8.1 as code-server
 FROM prom/prometheus:v2.29.2 as prom
-FROM prom/alertmanager:v0.23.0 as prom-am
+FROM prom/alertmanager:v0.31.1 as prom-am
 
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