Fix template expansion to allow spaces in template names

[HamishSlater]

Strict whitespace handling was recently introduced with #931

Trim to allow e.g. |+template = mytemplate

Alternatively, we could embrace the strictness, however docs should be updated:

https://www.semantic-mediawiki.org/wiki/Help:Datatables_format#Format_specific

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 45.39%. Comparing base (192c3eb) to head (661bd3d).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
formats/datatables/DataTables.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #945   +/-   ##
=========================================
  Coverage     45.39%   45.39%           
  Complexity     2326     2326           
=========================================
  Files            80       80           
  Lines          9078     9078           
=========================================
  Hits           4121     4121           
  Misses         4957     4957           

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