Update toc.yml

update name to match filename (changed to lcase to match repo)

Author: andrewconnell

docs/toc.yml

@@ -2084,7 +2084,7 @@
   - name: Application Lifecycle Management (ALM) APIs
     href: apis/alm-api-for-spfx-add-ins.md
   - name: CSOM methods for applying retention labels
-    href: apis/CSOM-methods-for-applying-retention-labels.md    
+    href: apis/csom-methods-for-applying-retention-labels.md    
   - name: SharePoint Add-in Management APIs
     href: apis/addin-management-apis.md
   - name: Microsoft 365 Copy and Move API