Initialize eri_gto to zero.

[AugustinLu]

This pull request adds zero initialization for variable eri_gto.

This solves #466

Results on Mac OS are now consistent with the reference value:
Conquest_out: |* Harris-Foulkes energy = -13.983024122321860 Ha
Conquest_out.ref: |* Harris-Foulkes energy = -13.983024122331756 Ha

[davidbowler]

I never saw this issue on MacOS but it's a sensible thing to do.

[AugustinLu]

(base) augustin@[MyMachine] % bash compare.sh
====================================================
 Conquest Version Comparison Workflow
 Old: ./Conquest_develop in Old/
 New: ./Conquest_fixed in New/
 MPI Processes: 2
====================================================

[1/3] Running Old version...
[2/3] Running New version...
[3/3] Comparing results...
----------------------------------------------------
 Metric         | Old Version | New Version
----------------------------------------------------
 SCF Iterations | 22          | 14
 Total Energy   | **-55403.462136901252961** | **-13.983024122316245**
----------------------------------------------------

CONCLUSION: The outputs differ.
====================================================

Fix confirmed.