Just corrected a small inconsistency on a doc page (#6603)
### Just corrected a small inconsistency on a doc page (not exactly a
typo, per se)
- Description: There was inconsistency due to the use of single quotes
at one place on the [Squential
Chains](https://python.langchain.com/docs/modules/chains/foundational/sequential_chains)
page of the docs,
- Issue: NA,
- Dependencies: NA,
- Tag maintainer: @dev2049,
- Twitter handle: kambleakash0
