[Bootstrap v5] Remove the custom form style

[rosier]

Most of the custom style has no effect since the form elements don't have a .form-group class anymore.

And the layout of textarea fields is broken by:

.form-control {
  height: 45px;
}

Since bootstrap already has style for the input fields that is almost identical I opted for removing the custom style

[javiereguiluz]

Less code to maintain 🙏 Thanks Jan!