Reduce log fatigue during startup.

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

.changeset/techdocs-search-log-fatigue.md

@@ -0,0 +1,6 @@
+---
+'@backstage/plugin-techdocs-backend': patch
+---
+
+Errors encountered while attempting to load TechDocs search indices at
+collation-time are now logged at `DEBUG` instead of `WARN` level.

plugins/techdocs-backend/src/search/DefaultTechDocsCollator.ts

@@ -110,7 +110,7 @@ export class DefaultTechDocsCollator implements DocumentCollator {
                   ?.target?.name || '',
             }));
           } catch (e) {
-            this.logger.warn(
+            this.logger.debug(
               `Failed to retrieve tech docs search index for entity ${entityInfo.namespace}/${entityInfo.kind}/${entityInfo.name}`,
               e,
             );