Remove duplicate word "the" (#326)

third_party/svgpan/svgpan.go

  * ======================
  *
  * Given an unique existing element with id "viewport" (or when missing, the
- * first g-element), including the the library into any SVG adds the following
+ * first g-element), including the library into any SVG adds the following
  * capabilities:
  *
  *  - Mouse panning