Remove newline in Textarea widget.

[python2and3developer]

The template of textarea widget has some extra spaces that are added directly inside the textarea when its rendering on the browser.
​https://github.com/django/django/blob/master/django/forms/templates/django/forms/widgets/textarea.html

<textarea name="{{ widget.name }}"{% include "django/forms/widgets/attrs.html" %}>
{% if widget.value %}{{ widget.value }}{% endif %}</textarea>

The proposal is to change that to this (only one line, instead of two):

<textarea name="{{ widget.name }}"{% include "django/forms/widgets/attrs.html" %}>{% if widget.value %}{{ widget.value }}{% endif %}</textarea>

[Mariusz Felisiak]

This newline is required to fix #8627.