Fix envcanada today pop

[eddiehung]

Fix for today's probability-of-precipitation weather module's envcanada provider.

Without which, requesting showPrecipitationProbability causes "undefined" to be shown.

Consistent with method used elsewhere in the file:
https://github.com/MichMich/MagicMirror/blob/abe5c08a52ffee6b37c30c1f3160e130f0e966a2/modules/default/weather/providers/envcanada.js#L395-L399

[codecov-commenter]

Codecov Report

Merging #3106 (69a12be) into develop (babd22b) will increase coverage by 0.04%.
The diff coverage is 0.00%.

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@@             Coverage Diff             @@
##           develop    #3106      +/-   ##
===========================================
+ Coverage    25.61%   25.65%   +0.04%     
===========================================
  Files           53       53              
  Lines        11427    11427              
===========================================
+ Hits          2927     2932       +5     
+ Misses        8500     8495       -5     

Impacted Files	Coverage Δ
modules/default/weather/providers/envcanada.js	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes