Apply backend maintainer feedback

lib/api/virtual_registries/packages/maven.rb

@@ -80,7 +80,7 @@ def registry
             desc 'Download endpoint of the Maven virtual registry.' do
               detail 'This feature was introduced in GitLab 17.3. \
                       This feature is currently in experiment state. \
-                      This feature behind the `virtual_registry_maven` feature flag.'
+                      This feature is behind the `virtual_registry_maven` feature flag.'
               success [
                 { code: 200 }
               ]
@@ -116,7 +116,7 @@ def registry
               desc 'Workhorse authorize upload endpoint of the Maven virtual registry. Only workhorse can access it.' do
                 detail 'This feature was introduced in GitLab 17.4. \
                         This feature is currently in experiment state. \
-                        This feature behind the `virtual_registry_maven` feature flag.'
+                        This feature is behind the `virtual_registry_maven` feature flag.'
                 success [
                   { code: 200 }
                 ]
@@ -142,7 +142,7 @@ def registry
               desc 'Workhorse upload endpoint of the Maven virtual registry. Only workhorse can access it.' do
                 detail 'This feature was introduced in GitLab 17.4. \
                         This feature is currently in experiment state. \
-                        This feature behind the `virtual_registry_maven` feature flag.'
+                        This feature is behind the `virtual_registry_maven` feature flag.'
                 success [
                   { code: 200 }
                 ]