Team Squad.xml
Line 82 in default files. Edit the row height.
<widget class="tactic_player_list_table" id="pltb" database_table_type="1" customisation_context="play" mode="fill_rows, stripe_rows, printable, store_sort_state, drag_rows, drop_on_rows, show_bullets, select_rows, select_multiple, show_insert_column_popup,keyboard" column_mode="resize_columns, move_columns, custom_views" popup_menu_class="popup_button_table_header" row_height="20" navigation_container="true" default_focus="true">
It'll be exactly the same in team squad tactics panel.xml, although a different line. Search for it easily by using the same id, just needs a bit of common sense to find.
If you don't have these files extract the base files using the resource archiver. If all of this is alien to you, you'll need to do some homework by reading the skinning guides.