Remove tui_erase_exec_info_content

Remove tui_erase_exec_info_content

One call to tui_erase_exec_info_content can be removed.  This call is
not needed because the function in question then immediately sets the
execution info window contents.

Once this is done, tui_clear_exec_info_content is just a wrapper for
the only call to tui_erase_exec_info_content, so
tui_erase_exec_info_content can be renamed and the wrapper function
removed.

gdb/ChangeLog
2019-08-13  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.h (tui_erase_exec_info_content): Don't
	declare.
	* tui/tui-winsource.c (tui_source_window_base::refresh_all): Don't
	call tui_erase_exec_info_content.
	(tui_clear_exec_info_content): Rename from
	tui_erase_exec_info_content.
	(tui_clear_exec_info_content): Delete.