feat-curate GPR for cysteine metabolism

[feiranl]

Main improvements in this PR:

Fix issues in #552

• remove gene ENSG00000083123 ENSG00000248098 ENSG00000091140 from rxn MAR06523
• remove gene ENSG00000168710 from rxn MAR03877 the model

I hereby confirm that I have:

• Tested my code on my own computer for running the model
• Selected develop as a target branch
• Any removed reactions and metabolites have been moved to the corresponding deprecated identifier lists

[haowang-bioinfo]

AHCYL1 (ENSG00000168710) is annotated as Multifaceted cellular regulator and hows no hydrolase activity to SAH, probably should be removed from the model?

Everything else is fine - good work

[feiranl]

@haowang-bioinfo it says In spite of its similarity with AHCY, which catalyzes the reversible hydrolysis of S-adenosyl-L-homocysteine to adenosine and homocysteine, recombinant AHCYL1 expressed in bacteria shows no hydrolase activity, nor does it affect the enzyme activity of AHCY, thus, I decided to remove it.

[haowang-bioinfo]

thus, I decided to remove it.

agree, go ahead to remove it

[feiranl]

I see your point, you mean not only remove the gene from the rxn, but remove the gene totally from the model. Done!