Fix multi-gpu training error for LayoutLMv2
Author: akkikiki
Pull request: yes

# What does this PR do?

Fixes #14110

## Issue

When training a LayoutLMv2 model with multiple GPUs using `torchrun --standalone --nnodes=1 --nproc_per_node=$NUM_GPUS run_layoutlmv2.py` (single node, multi-gpu), I encounter 

```
RuntimeError: Make sure the number of processes can be divided by the number of nodes
```

## What this PR fixes
Fixes a one character typo/bug to run using multiple GPUs

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

cc @amyeroberts