[PULL REQUEST] Remove duplicate Inst%FLUXSABI allocation in MEGAN HCO extension

[jimmielin]

Hi GCST,

This is a minor fix sent to me from Thibaud Fritz from MIT (@fritzt). He wrote:

I found what seems to be a minor bug/typo in HEMCO Extensions. In hcox_megan_mod.F90, Inst%FLUXSABI seems to get allocated twice which I don't see a reason why this is the case.

HEMCO/src/Extensions/hcox_megan_mod.F90

Lines 4065 to 4077 in f2e5f9b

	ALLOCATE( Inst%FLUXSABI( NX, NY ), STAT=AS )
	IF ( AS /= 0 ) THEN
	CALL HCO_ERROR( HcoState%Config%Err, 'FLUXBPIN', RC )
	RETURN
	ENDIF
	Inst%FLUXBPIN = 0.0_sp
	ALLOCATE( Inst%FLUXSABI( NX, NY ), STAT=AS )
	IF ( AS /= 0 ) THEN
	CALL HCO_ERROR( HcoState%Config%Err, 'FLUXSABI', RC )
	RETURN
	ENDIF
	Inst%FLUXSABI = 0.0_sp

This PR removes the duplicate allocation. Thanks!