Debian 11 pbuilder build failure - libgranite version issue?

## What Happened
Attempting to build using pbuilder for Debian 11 Bullseye using tasks-6.0.2.tar.gz and tasks_6.0.2-debian.tar.gz under releases fails.

## Expected Behavior
Build completes without issue if the dependencies listed in the the README and debian/control file are correct.

## Steps to Reproduce
Attempt pbuilder build for Debian 11 Bullseye using tasks-6.0.2.tar.gz and tasks_6.0.2-debian.tar.gz under releases
`OS=debian DIST=bullseye ARCH=amd64 pdebuild --debbuildopts "-sa -jauto"`

I've been hitting similar issues with a bunch of Apps that use granite, assuming at this point libgranite6 is needed, which is still in Experimental due to the freeze, and will probably only make it's way to Sid after quite awhile after Bullseye release.

### Logs
```
FAILED: io.elementary.tasks.p/obj-x86_64-linux-gnu/Config.c io.elementary.tasks.p/src/Application.c io.elementary.tasks.p/src/Location.c io.elementary.tasks.p/src/MainWindow.c io.elementary.tasks.p/src/Util.c io.elementary.tasks.p/src/Widgets/EditableLabel.c io.elementary.tasks.p/src/Widgets/EntryPopover/DateTime.c io.elementary.tasks.p/src/Widgets/EntryPopover/Generic.c io.elementary.tasks.p/src/Widgets/EntryPopover/Location.c io.elementary.tasks.p/src/Widgets/ListView.c io.elementary.tasks.p/src/Widgets/ScheduledRow.c io.elementary.tasks.p/src/Widgets/SourceRow.c io.elementary.tasks.p/src/Widgets/TaskRow.c io.elementary.tasks.p/src/Widgets/ListSettingsPopover.c io.elementary.tasks.p/src/TaskModel.c
valac -C /build/tasks-6.0.2/vapi/libecal-2.0-fixes.vapi --pkg libgdata --pkg libical-glib --pkg libhandy-1 --pkg libgeoclue-2.0 --pkg libedataserver-1.2 --pkg libecal-2.0 --pkg gtk+-3.0 --pkg granite --pkg gobject-2.0 --pkg glib-2.0 --pkg geocode-glib-1.0 --pkg clutter-gtk-1.0 --pkg clutter-1.0 --pkg champlain-gtk-0.12 --pkg champlain-0.12 --color=always --directory io.elementary.tasks.p --basedir ../ --gresources=../data/gresource.xml Config.vala ../src/Application.vala ../src/Location.vala ../src/MainWindow.vala ../src/Util.vala ../src/Widgets/EditableLabel.vala ../src/Widgets/EntryPopover/DateTime.vala ../src/Widgets/EntryPopover/Generic.vala ../src/Widgets/EntryPopover/Location.vala ../src/Widgets/ListView.vala ../src/Widgets/ScheduledRow.vala ../src/Widgets/SourceRow.vala ../src/Widgets/TaskRow.vala ../src/Widgets/ListSettingsPopover.vala ../src/TaskModel.vala
libgdata.vapi:2012.3-2012.27: warning: Creation method of abstract class cannot be public.
public Parsable.from_json (GLib.Type parsable_type, string json, int length) throws GLib.Error;
^^^^^^^^^^^^^^^^^^^^^^^^^
libgdata.vapi:2015.3-2015.26: warning: Creation method of abstract class cannot be public.
public Parsable.from_xml (GLib.Type parsable_type, string xml, int length) throws GLib.Error;
^^^^^^^^^^^^^^^^^^^^^^^^
../src/Widgets/ListSettingsPopover.vala:114.41-114.65: error: The name `SwitchModelButton' does not exist in the context of `Granite' (granite)
var show_completed_button = new Granite.SwitchModelButton (_("Show Completed")) {
^^^^^^^^^^^^^^^^^^^^^^^^^
Compilation failed: 1 error(s), 2 warning(s)
ninja: build stopped: subcommand failed.
dh_auto_build: error: cd obj-x86_64-linux-gnu && LC_ALL=C.UTF-8 ninja -j1 -v returned exit code 1
make: *** [debian/rules:13: build] Error 25
dpkg-buildpackage: error: debian/rules build subprocess returned exit status 2
I: copying local configuration
E: Failed autobuilding of package
```

## Platform Information
* Debian 11 Bullseye Pre-Release

If anything it would be nice to have the README or debian/control file updated with specific build depends and runtime dependency versions (vala and granite probably the most important).
If it's a matter or just needing libgranite6, that at least lets us know that this and all the other troublesome apps are going to have to wait until libgranite6 can be fully tested and backporting is known and good. Thanks for any input.