Add missing Grant import to townsquare/utils

[androolloyd]

Description

townsquare/utils has a helper can_pin to check for permission to create/update/delete a pin, the grant import was missing.

Refers/Fixes

Bug found by @owocki

Testing

[codecov]

Codecov Report

Merging #6693 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #6693   +/-   ##
=======================================
  Coverage   27.12%   27.12%           
=======================================
  Files         291      291           
  Lines       27115    27115           
  Branches     3989     3989           
=======================================
  Hits         7354     7354           
+ Misses      19493    19488    -5     
- Partials      268      273    +5     

Impacted Files	Coverage Δ
app/townsquare/views.py	9.86% <ø> (-0.20%)	⬇️
app/townsquare/utils.py	18.18% <100.00%> (+2.55%)	⬆️
app/quests/views.py	16.22% <0.00%> (ø)
app/dashboard/views.py	10.93% <0.00%> (ø)
...rketing/management/commands/no_applicants_email.py	0.00% <0.00%> (ø)
...eting/management/commands/assemble_leaderboards.py	40.05% <0.00%> (ø)

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