docs: fix spelling

Author: KyleTryon

src/examples/create_review_app.yml

@@ -1,5 +1,5 @@
 description: >
-  A sample job that deploys a review app to Herou, that does not run on the main
+  A sample job that deploys a review app to Heroku, that does not run on the main
   "deployed" branch. Assumes that your CircleCI token is stored in $CIRCLECI_API_KEY
   and Heroku's API key under $HEROKU_API_KEY.
 usage:

src/jobs/deploy-via-git.yml

@@ -12,7 +12,7 @@ parameters:
     default: $HEROKU_APP_NAME
   maintenance-mode:
     description:
-      "Use this to automatically enable mantainance mode before pre-deploy steps
+      "Use this to automatically enable maintenance mode before pre-deploy steps
         and have it disabled after post-deploy steps have been run."
     type: boolean
     default: false

src/jobs/push-docker-image.yml

@@ -12,7 +12,7 @@ parameters:
     default: $HEROKU_APP_NAME
   maintenance-mode:
     description:
-      "Use this to automatically enable mantainance mode before pre-deploy steps
+      "Use this to automatically enable maintenance mode before pre-deploy steps
         and have it disabled after post-deploy steps have been run."
     type: boolean
     default: false