[FE] BE_URL - Delete empty space between host and port

[elfro]

BE_URL has the wrong value, cuz REACT_APP_BE_URL might be imported with one extra space in the end of the string.

Branch: GH-47-add-missing-ros-events

STR:

1. Open FE app in the browser
2. Click on 'Play' icon

Actual result: the following request is failed:

method: POST
url: `${BE_URL}/offer`

Expected result: URL should be valid and request should pass successfully