fix small spelling mistake

ui/aboutdialog.ui

@@ -89,7 +89,7 @@
         </sizepolicy>
        </property>
        <property name="text">
-        <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;span style=&quot; font-size:24pt; font-weight:600;&quot;&gt;Chordsheet&lt;/span&gt;&lt;br/&gt;by Ivan Holmes&lt;/p&gt;&lt;p&gt;Chordsheet is a piece of software that generates a chord sheet with a simple GUI. &lt;/p&gt;&lt;p&gt;&lt;a href=&quot;https://github.com/ivanholmes/chordsheet&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#0000ff;&quot;&gt;Github&lt;/span&gt;&lt;/a&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+        <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;&lt;span style=&quot; font-size:24pt; font-weight:600;&quot;&gt;Chordsheet&lt;/span&gt;&lt;br/&gt;by Ivan Holmes&lt;/p&gt;&lt;p&gt;Chordsheet is a piece of software that generates a chord sheet with a simple GUI. &lt;/p&gt;&lt;p&gt;&lt;a href=&quot;https://github.com/ivanholmes/chordsheet&quot;&gt;&lt;span style=&quot; text-decoration: underline; color:#0000ff;&quot;&gt;GitHub&lt;/span&gt;&lt;/a&gt;&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
        </property>
        <property name="alignment">
         <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>