Missing backslash in \code{} markup

[aitap]

Two backslashes were forgotten in a recent PR, giving a NOTE:

* checking Rd files ... NOTE
checkRd: (-1) fctr.Rd:6: Lost braces
     6 |   Creates a code{\link[base:factor]{factor}}.
       |                 ^
checkRd: (-1) fctr.Rd:16: Lost braces
    16 |   \item{\dots}{ Other arguments passed to code{\link[base:factor]{factor}}. }
       |                                               ^

2b4b3ed is only there because I consider this style more DRY, but it can be reverted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@            Coverage Diff            @@
##             master    #7114   +/-   ##
=========================================
  Coverage          ?   98.50%           
=========================================
  Files             ?       79           
  Lines             ?    14754           
  Branches          ?        0           
=========================================
  Hits              ?    14533           
  Misses            ?      221           
  Partials          ?        0           

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