docs(install-monolithic): add quotation marks (#12982)

Co-authored-by: Michel Hollands <[email protected]>

Author: choeffer

docs/sources/setup/install/helm/install-monolithic/_index.md

@@ -47,7 +47,7 @@ If you set the `singleBinary.replicas` value to 2 or more, this chart configures
           type: 'filesystem'
         schemaConfig:
           configs:
-          - from: 2024-01-01
+          - from: "2024-01-01"
             store: tsdb
             index:
               prefix: loki_index_
@@ -72,7 +72,7 @@ If you set the `singleBinary.replicas` value to 2 or more, this chart configures
           replication_factor: 3
         schemaConfig:
           configs:
-          - from: 2024-01-01
+          - from: "2024-01-01"
             store: tsdb
             index:
               prefix: loki_index_