chore(deps): update prom/memcached-exporter docker tag to v0.15.0 (#13860)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Trevor Whitney <trevorjwhitney@gmail.com>

Author: renovate[bot]

docs/sources/setup/install/helm/reference.md

@@ -6802,7 +6802,7 @@ true
 			<td>string</td>
 			<td></td>
 			<td><pre lang="json">
-"v0.14.2"
+"v0.15.0"
 </pre>
 </td>
 		</tr>

production/helm/loki/values.yaml

@@ -3031,7 +3031,7 @@ memcachedExporter:
   enabled: true
   image:
     repository: prom/memcached-exporter
-    tag: v0.14.2
+    tag: v0.15.0
     pullPolicy: IfNotPresent
   resources:
     requests: {}