RNAProduct: fix typo in docstrings
RNAProduct: fix typo in docstrings

james-monkeyshines/ensembl,Ensembl/ensembl,Ensembl/ensembl,muffato/ensembl,james-monkeyshines/ensembl,muffato/ensembl,muffato/ensembl,Ensembl/ensembl,Ensembl/ensembl,james-monkeyshines/ensembl,muffato/ensembl,james-monkeyshines/ensembl