[Create term modal] Creation and Updating validation issues.

**Environment:** All browsers.
**Reproducible:** always.
**Build found:** commit https://github.com/ita-social-projects/StreetCode_Client/commit/76687e96efa660445ddd703d9499dbe2f7179011

**Preconditions**
Loaded project.

**Steps to reproduce**
1. Go to http://localhost:3000/admin-panel/dictionary
2. Click on "Новий термін" button.
3. Click on "Зберегти" button.

**Actual result**
The empty row was added as a new term.

**Expected result**
The form should not be submitted before the user entered the valid input. The fields should be required.

**Postconditions**
No specific post conditions.

**User story and test case links**
[Epic #2](https://github.com/ita-social-projects/StreetCode/issues/114)