Clarify use of the term "OTF"

- change button tooltip from referring to "OTFR" to "OTF" to match
button text
- change wording of enable CRS transformation option to make it
more obvious that this option is what "OTF" refers to

Inspired by @rouault

src/app/qgisapp.cpp

@@ -9704,13 +9704,13 @@ void QgisApp::updateCRSStatusBar()
   {
     mOnTheFlyProjectionStatusButton->setText( tr( "%1 (OTF)" ).arg( mOnTheFlyProjectionStatusButton->text() ) );
     mOnTheFlyProjectionStatusButton->setToolTip(
-      tr( "Current CRS: %1 (OTFR enabled)" ).arg( mMapCanvas->mapSettings().destinationCrs().description() ) );
+      tr( "Current CRS: %1 (OTF enabled)" ).arg( mMapCanvas->mapSettings().destinationCrs().description() ) );
     mOnTheFlyProjectionStatusButton->setIcon( QgsApplication::getThemeIcon( "mIconProjectionEnabled.png" ) );
   }
   else
   {
     mOnTheFlyProjectionStatusButton->setToolTip(
-      tr( "Current CRS: %1 (OTFR disabled)" ).arg( mMapCanvas->mapSettings().destinationCrs().description() ) );
+      tr( "Current CRS: %1 (OTF disabled)" ).arg( mMapCanvas->mapSettings().destinationCrs().description() ) );
     mOnTheFlyProjectionStatusButton->setIcon( QgsApplication::getThemeIcon( "mIconProjectionDisabled.png" ) );
   }
 }