Use less alarming fee warning note (#3038)

Author: UdjinM6

src/qt/forms/sendcoinsdialog.ui

@@ -771,7 +771,7 @@
             </font>
             </property>
             <property name="text">
-             <string>Warning: Fee estimation is currently not possible.</string>
+             <string>Note: Not enough data for fee estimation, using the fallback fee instead.</string>
             </property>
             <property name="wordWrap">
              <bool>false</bool>

src/qt/sendcoinsdialog.cpp

@@ -750,9 +750,6 @@ void SendCoinsDialog::updateSmartFeeLabel()
         ui->labelSmartFee2->show(); // (Smart fee not initialized yet. This usually takes a few blocks...)
         ui->labelFeeEstimation->setText("");
         ui->fallbackFeeWarningLabel->setVisible(true);
-        int lightness = ui->fallbackFeeWarningLabel->palette().color(QPalette::WindowText).lightness();
-        QColor warning_colour(255 - (lightness / 5), 176 - (lightness / 3), 48 - (lightness / 14));
-        ui->fallbackFeeWarningLabel->setStyleSheet("QLabel { color: " + warning_colour.name() + "; }");
         ui->fallbackFeeWarningLabel->setIndent(QFontMetrics(ui->fallbackFeeWarningLabel->font()).width("x"));
     }
     else