Update env.sh so that is does not error when running on Mac

[bddicken]

Description

This is a minor fix to examples/common/env.sh so that it does not error out on mac where zsh is the default shell. shopt is bash-specific and does not work on zsh. This fix was suggested by @mattlord while reviewing and discussing this other PR for the docs on the website: https://github.com/vitessio/website/pull/1736

This is my first PR to vitessio/vitess so not sure about other procedures such as backports, etc.

Related Issue(s)

No issue for this.

Checklist

• [x] "Backport to:" labels have been added if this change should be back-ported to release branches
• [x] If this change is to be back-ported to previous releases, a justification is included in the PR description
• [x] Tests were added or are not required
• [x] Did the new or modified tests pass consistently locally and on CI?
• [x] Documentation was added or is not required

[vitess-bot[bot]]

Review Checklist

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[frouioui]

This is my first PR to vitessio/vitess so not sure about other procedures such as backports, etc.

I would vote for backporting this to previous release branches as people can use the getting started guide / examples from any branch while reading the docs.

[bddicken]

I apologize for the delay! I guess we missed the backport deadline for the releases earlier this week.

Anyways, PR has been updated with the fix recommended my @mattlord.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 68.43%. Comparing base (f118ba2) to head (2c6ae26). Report is 82 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15835      +/-   ##
==========================================
+ Coverage   68.40%   68.43%   +0.02%     
==========================================
  Files        1556     1559       +3     
  Lines      195121   196825    +1704     
==========================================
+ Hits       133479   134702    +1223     
- Misses      61642    62123     +481     

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