Update preprocessing.md

Corrected small spelling mistake

docs/preprocessing.md

@@ -11,7 +11,7 @@ The important files that this pipeline produces that are needed in DeepRVAT are:
 
 - **preprocessed/genotypes.h5** *The main sparse hdf5 file*
 
-- **norm/variants/variants.parquet** *List of variants i parquet format*
+- **norm/variants/variants.parquet** *List of variants in parquet format*
 
 ## Setup environment
 
@@ -229,4 +229,4 @@ After configuration and activating the environment run the pipeline using snakem
 
 ```shell
 snakemake -j<nr_cores> --configfile config/deeprvat_preprocess_config.yaml -s preprocess_no_qc.snakefile  
-```
+```