configure: Remove manual pthread configuration
configure: Remove manual pthread configuration

The PTHREAD_{CFLAGS,LIBS} are no longer directly required by our test
files so we don't need to explicitly depend on it. Instead, pull in the
macro so that googletest is configured correctly.

Tested:
    Builds and run through the unit-test scripts. Pthread support is
    still detected when it is needed.

Change-Id: I4c24177f930ea6c104c69a06ac3fdf0b5ae1535a
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus,openbmc/sdbusplus