Address a few sphinx warnings

[rahulporuri]

Not sure if this is the right fix but this is a fix. This PR addresses the following sphinx warnings :

pyface\tasks\tasks_application.py:docstring of pyface.tasks.tasks_application.TaskFactory.factory:3: WARNING: Inline strong start-string without end-string.
pyface\timer\do_later.py:docstring of pyface.timer.do_later.do_later:5: WARNING: Inline strong start-string without end-string.
pyface\timer\do_later.py:docstring of pyface.timer.do_later.do_later:6: WARNING: Inline strong start-string without end-string.
pyface\timer\do_later.py:docstring of pyface.timer.do_later.do_after:7: WARNING: Inline strong start-string without end-string.
pyface\timer\do_later.py:docstring of pyface.timer.do_later.do_after:8: WARNING: Inline strong start-string without end-string.

Interpreting the "Inline strong start-string" as "**", the fix I employed was to simply escape the characters i.e. "\**"

[codecov-io]

Codecov Report

Merging #846 (3634f94) into master (92ab736) will increase coverage by 0.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #846      +/-   ##
==========================================
+ Coverage   41.15%   41.29%   +0.13%     
==========================================
  Files         522      522              
  Lines       28110    28123      +13     
  Branches     4251     4253       +2     
==========================================
+ Hits        11568    11612      +44     
+ Misses      16037    16014      -23     
+ Partials      505      497       -8     

Impacted Files	Coverage Δ
pyface/action/action_manager.py	83.92% <ø> (ø)
pyface/tasks/tasks_application.py	56.94% <ø> (ø)
pyface/timer/do_later.py	100.00% <ø> (ø)
pyface/resource/resource_manager.py	59.32% <100.00%> (+7.89%)	⬆️
pyface/ui/qt4/console/console_widget.py	28.86% <0.00%> (+0.31%)	⬆️
pyface/ui/qt4/code_editor/code_widget.py	43.55% <0.00%> (+0.84%)	⬆️
pyface/wx/python_stc.py	10.36% <0.00%> (+1.21%)	⬆️
pyface/ui/qt4/tasks/task_window_backend.py	60.52% <0.00%> (+1.31%)	⬆️
pyface/ui/qt4/util/gui_test_assistant.py	80.53% <0.00%> (+2.65%)	⬆️
... and 5 more

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[kitchoi]

Confirmed the warnings in timer package are gone. The rendered doc still looks a bit odd but this PR has not made it worse.