fdo#75757: remove inheritance to std::map

Change-Id: I9dfabddf4b51994c1ae078582dec3f385e7d1a5c
Reviewed-on: https://gerrit.libreoffice.org/12513
Reviewed-by: Takeshi Abe <tabe@fixedpoint.jp>
Tested-by: Takeshi Abe <tabe@fixedpoint.jp>