fix issue with json unmarshalling of operators with space in them

[systay]

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.

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Backward compatibility

• Protobuf changes should be wire-compatible.
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• vtctl command output order should be stable and awk-able.

[frouioui]

LGTM, TestVExplainKeys is failing due to missing backticks

[codecov]

Codecov Report

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

Project coverage is 69.42%. Comparing base (2cef46e) to head (59527d0).
Report is 1 commits behind head on main.

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             @@
##             main   #16905      +/-   ##
==========================================
- Coverage   69.43%   69.42%   -0.01%     
==========================================
  Files        1570     1570              
  Lines      203798   203812      +14     
==========================================
- Hits       141498   141488      -10     
- Misses      62300    62324      +24     

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