docs(transactions): fix addIndex example and grammar (#11759)

docs/manual/migrations.md

@@ -258,7 +258,7 @@ module.exports = {
 };
 };
 ```
 ```
 
 
-The next is an example of a migration that has a foreign key. You can use references to specify a foreign key:
+The next example is of a migration that has a foreign key. You can use references to specify a foreign key:
 
 
 ```js
 ```js
 module.exports = {
 module.exports = {
@@ -291,7 +291,7 @@ module.exports = {
 
 
 ```
 ```
 
 
-The next is an example of a migration that has uses async/await where you create an unique index on a new column:
+The next example is of a migration that uses async/await where you create an unique index on a new column:
 
 
 ```js
 ```js
 module.exports = {
 module.exports = {
@@ -312,8 +312,8 @@ module.exports = {
         {
         {
           fields: 'petName',
           fields: 'petName',
           unique: true,
           unique: true,
-        },
-        { transaction }
+          transaction,
+        }
       );
       );
       await transaction.commit();
       await transaction.commit();
     } catch (err) {
     } catch (err) {