Removed unwanted call to pj_log_level().

When running the self-test with logging was turned off globally when
the PJ_cart test was run. As a consequence all test functions
called after PJ_cart was not able to output debugging information.
In most cases this would go by unnoticed but when calling proj with
PROJ_DEBUG=1 (or higher) all debugging output whould get suppressed.

This commit removes the call to pj_log_level that turns of debugging
output in the self-test.

src/PJ_cart.c

@@ -252,9 +252,6 @@ int pj_cart_selftest (void) {
     if (0==P)
         return 2;
 
-    /* Turn off logging */
-    pj_log_level (0, PJ_LOG_NONE);
-
     /* zero initialize everything, then set (longitude, latitude) to (12, 55) */
     a = pj_obs_null;
     /* a.coo.lp: The coordinate part of a, interpreted as a classic LP pair */