[Rd] Typo in grep.Rd

[Martin Maechler]

>>>>> Korpela Mikko (MML) 
>>>>>     on Sat, 8 Dec 2018 17:43:05 +0000 writes:

    > There is a small typo in file 'src/library/base/man/grep.Rd'.
    > Current text:
    > ## collation order is aAbBcCdEe ...

    > Suggested text ("D" instead of "E"):
    > ## collation order is aAbBcCdDe ...

Indeed, now fixed.  Thank you Mikko!
Martin