docs: Remove double quotes(") at quickstart.md

[mysticrenji]

-> run aks-engine deploy example script contains unwanted (") at Line number 84 of Quickstart.md, which causes syntax error. I have tried the script after truncating " and it runs successfully.

Reason for Change:
run aks-engine deploy example script contains unwanted (") at Line number 84 of Quickstart.md, which causes syntax error. I have tried the script after truncating " and it runs successfully.

Issue Fixed:
Cosmetic changes in the Quickstart.md

Credit Where Due:

Does this change contain code from or inspired by another project?

• [X ] No
• Yes

If "Yes," did you notify that project's maintainers and provide attribution?

• [X ] No
• Yes

Requirements:

• uses docs: Documentation 📘
• [ X] includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[welcome]

💖 Thanks for opening your first pull request! 💖 We use semantic commit messages to streamline the release process. Before your pull request can be merged, you should make sure your first commit and PR title start with a semantic prefix. Examples of commit messages with semantic prefixes: - fix: change azure disk cachingMode to ReadOnly - feat: make maximumLoadBalancerRuleCount configurable - docs: add note on AKS Engine and AKS relationship
Make sure to check out the developer guide for guidance on testing your change.

[mysticrenji]

/assign @ritazh

[jackfrancis]

/lgtm

[jackfrancis]

Thx @mysticrenji!

[welcome]

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