initial memleak fix attempts

[pstjohn]

Running training with

DATA_DIR=$(download_bionemo_data esm2/testdata_esm2_pretrain:2.0 --source pbss)

python scripts/protein/esm2/esm2_pretrain.py \
    --train-cluster-path ${DATA_DIR}/2024_03_sanity/train_clusters_sanity.parquet \
    --train-database-path ${DATA_DIR}/2024_03_sanity/train_sanity.db \
    --valid-cluster-path ${DATA_DIR}/2024_03_sanity/valid_clusters.parquet \
    --valid-database-path ${DATA_DIR}/2024_03_sanity/validation.db \
    --precision="bf16-mixed" \
    --num-gpus 1 \
    --num-nodes 1 \
    --num-steps 100 \
    --val-check-interval 100 \
    --max-seq-length 1024 \
    --min-seq-length 1024 \
    --limit-val-batches 2 \
    --micro-batch-size 2 \
    --num-layers 33 \
    --hidden-size 1280 \
    --num-attention-head 20 \
    --ffn-hidden-size 5120