Revert "Make the output window readonly, but still keyboard friendly"

This reverts commit 3080d0d9e7.

Having the output pane editable is considered a feature by some as
it allows easy modification of the contents before passing into
other, less accessible interfaces, like Gerrit comment fields.

Task-number: QTCREATORBUG-18418
Change-Id: Ice0c6c5e5787d242c714a7b0f61559a70d25d243
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Vikas Pachdha <vikas.pachdha@qt.io>

src/libs/utils/outputformatter.cpp

@@ -68,8 +68,6 @@ QPlainTextEdit *OutputFormatter::plainTextEdit() const
 
 void OutputFormatter::setPlainTextEdit(QPlainTextEdit *plainText)
 {
-    plainText->setReadOnly(true);
-    plainText->setTextInteractionFlags(plainText->textInteractionFlags() | Qt::TextSelectableByKeyboard);
     d->plainTextEdit = plainText;
     d->cursor = plainText ? plainText->textCursor() : QTextCursor();
     initFormats();