fix typo

Author: sl-solution

docs/src/man/gallery.md

@@ -114,8 +114,7 @@ julia> byrow(ds, fill!, :, with = byrow(ds, coalesce, :), rolling = true)
   10 │        1         1         3         1         1         3
 ```
 
-* [A use-case from practice](https://www.juliabloggers.com/news-features-in-dataframes-jl-1-3-part-1/) : We have a data frame
-that has 10,000 rows and columns, but this time we have 50% of missing values
+* [A use-case from practice](https://www.juliabloggers.com/news-features-in-dataframes-jl-1-3-part-1/) : We have a data frame that has 10,000 rows and columns, but this time we have 50% of missing values
 randomly scattered in it. What we want to do is to fill missing values in each
 row with row means of non-missing values.