Update build_guide.rst

typo

docs/source/build_guide.rst

@@ -268,7 +268,7 @@ Printing
 
 These pieces will print without supports in the orientation shown in the photos.  I use 3 perimeter layers and 15% infill, but the pieces are not large and don't need to handle heavy forces so almost any print settings should work.
 
-You will want to consider using a material other than PLA, as your PiFinder is likely to experience some sunlight in it's lifetime and PLA degrades under moderate heat and UV.  PETG or some co-polymer like NGen would be a good choice.  Prusamint Galaxy PETG is the official PiFinder filament and is pictured in most of the build guide, except where grey provided needed contrast.
+You will want to consider using a material other than PLA, as your PiFinder is likely to experience some sunlight in it's lifetime and PLA degrades under moderate heat and UV.  PETG or some co-polymer like NGen would be a good choice.  Prusament Galaxy PETG is the official PiFinder filament and is pictured in most of the build guide, except where grey provided needed contrast.
 
 Inserts
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