It's called an "Integration Manager" (singular)

Fixes https://github.com/vector-im/riot-web/issues/11256

This was finally annoying me enough to fix it.

res/css/_components.scss

@@ -172,7 +172,7 @@
 @import "./views/rooms/_WhoIsTypingTile.scss";
 @import "./views/settings/_DevicesPanel.scss";
 @import "./views/settings/_EmailAddresses.scss";
-@import "./views/settings/_IntegrationsManager.scss";
+@import "./views/settings/_IntegrationManager.scss";
 @import "./views/settings/_KeyBackupPanel.scss";
 @import "./views/settings/_Notifications.scss";
 @import "./views/settings/_PhoneNumbers.scss";

res/css/views/dialogs/_TermsDialog.scss

@@ -16,10 +16,10 @@ limitations under the License.
 
 /*
  * To avoid visual glitching of two modals stacking briefly, we customise the
- * terms dialog sizing when it will appear for the integrations manager so that
+ * terms dialog sizing when it will appear for the integration manager so that
  * it gets the same basic size as the IM's own modal.
  */
-.mx_TermsDialog_forIntegrationsManager .mx_Dialog {
+.mx_TermsDialog_forIntegrationManager .mx_Dialog {
     width: 60%;
     height: 70%;
     box-sizing: border-box;

res/css/views/settings/_IntegrationManager.scss

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-.mx_IntegrationsManager .mx_Dialog {
+.mx_IntegrationManager .mx_Dialog {
     width: 60%;
     height: 70%;
     overflow: hidden;
@@ -23,22 +23,22 @@ limitations under the License.
     max-height: initial;
 }
 
-.mx_IntegrationsManager iframe {
+.mx_IntegrationManager iframe {
     background-color: #fff;
     border: 0px;
     width: 100%;
     height: 100%;
 }
 
-.mx_IntegrationsManager_loading h3 {
+.mx_IntegrationManager_loading h3 {
     text-align: center;
 }
 
-.mx_IntegrationsManager_error {
+.mx_IntegrationManager_error {
     text-align: center;
     padding-top: 20px;
 }
 
-.mx_IntegrationsManager_error h3 {
+.mx_IntegrationManager_error h3 {
     color: $warning-color;
 }