[release-21.0] fix issue with json unmarshalling of operators with space in them

[systay]

This is a backport of #16905

Description

In a PR merged earlier today, I accidentally failed to consider binary operators that have spaces in them, such as not like and not in. This is a fix for that oversight.

Related Issue(s)

#16892

Checklist

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

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
• Ensure there is a link to an issue (except for internal cleanup and flaky test fixes), new features should have an RFC that documents use cases and test cases.

Tests

• Bug fixes should have at least one unit or end-to-end test, enhancement and new features should have a sufficient number of tests.

Documentation

• Apply the release notes (needs details) label if users need to know about this change.
• New features should be documented.
• There should be some code comments as to why things are implemented the way they are.
• There should be a comment at the top of each new or modified test to explain what the test does.

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• If the workflow needs to be marked as required, the maintainer team must be notified.

Backward compatibility

• Protobuf changes should be wire-compatible.
• Changes to _vt tables and RPCs need to be backward compatible.
• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 57.14286% with 15 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-21.0@1634894). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
go/vt/sqlparser/ast_funcs.go	33.33%	10 Missing ⚠️
go/vt/vtgate/planbuilder/operators/keys.go	75.00%	5 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             release-21.0   #16933   +/-   ##
===============================================
  Coverage                ?   69.41%           
===============================================
  Files                   ?     1570           
  Lines                   ?   203812           
  Branches                ?        0           
===============================================
  Hits                    ?   141484           
  Misses                  ?    62328           
  Partials                ?        0           

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