tst_textarea: fix warnings

Fix all warnings encountered in test run:

- in test_alignment()
QWARN Could not set initial property horizontalAlignment

- in test_flickable():
QWARN Setting initial properties failed: QQuickFlickable does not have a
property called selectByMouse
QWARN Setting initial properties failed: QQuickFlickable does not have a
property called text

- in test_font_explicit_attributes(family)
QWARN qt.qpa.fonts: Populating font family aliases took 130 ms. Replace
uses of missing font family "Courier" with one that exists to avoid this
cost.

Fixes: QTBUG-119645
Task-number: QTBUG-99231
Pick-to: 6.6 6.5
Change-Id: I9939286c46eebc188610ee0b09350be8dda833b3
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>
(cherry picked from commit ea3d7ec08b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

tests/auto/quickcontrols/controls/data/tst_textarea.qml

@@ -207,10 +207,12 @@ TestCase {
     }
 
     function test_alignment(data) {
-        var control = createTemporaryObject(textArea, testCase, {text: data.text, placeholderText: data.placeholderText, horizontalAlignment: data.textAlignment})
+        var control = createTemporaryObject(textArea, testCase, {text: data.text, placeholderText: data.placeholderText})
 
-        if (data.textAlignment !== undefined)
+        if (data.textAlignment !== undefined) {
+            control.horizontalAlignment = data.textAlignment
             compare(control.horizontalAlignment, data.textAlignment)
+        }
 
         // The placeholder text of the Material style doesn't currently respect the alignment of the control.
         if (StyleInfo.styleName !== "Material") {
@@ -234,7 +236,7 @@ TestCase {
         return [
             {tag: "bold", value: true},
             {tag: "capitalization", value: Font.Capitalize},
-            {tag: "family", value: "Courier"},
+            {tag: "family", value: "Tahoma"},
             {tag: "italic", value: true},
             {tag: "strikeout", value: true},
             {tag: "underline", value: true},
@@ -272,7 +274,7 @@ TestCase {
     }
 
     function test_flickable() {
-        var control = createTemporaryObject(flickable, testCase, {text:"line0", selectByMouse: true})
+        var control = createTemporaryObject(flickable, testCase)
         verify(control)
 
         var textArea = control.TextArea.flickable