Fix a rendering issue in the geo envelope docs. (#42332)

Previously the formatting information didn't display in the docs, and the
sentence just rendered as "bounding rectangle in the format :".

Author: jtibshirani

docs/reference/mapping/types/geo-shape.asciidoc

@@ -617,7 +617,7 @@ POST /example/doc
 
 Elasticsearch supports an `envelope` type, which consists of coordinates
 for upper left and lower right points of the shape to represent a
-bounding rectangle in the format [[minLon, maxLat],[maxLon, minLat]]:
+bounding rectangle in the format `[[minLon, maxLat], [maxLon, minLat]]`:
 
 [source,js]
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