expr: switch off left push down due to intergration test failed

[Yisaer]

What problem does this PR solve?

Issue Number: close #33255 #33256

Problem Summary:

What is changed and how it works?

switch off left push down due to intergration test failed which block 6.0 release. After we find out bug, we will switch on left push down again

I run mysql-test with this request, the result is expected.

$ ./mysql_test -host 127.0.0.1 -port 4000 -user root -params '&allowNativePasswords=true&allowAllFiles=true' index_merge_sqlgen_exprs_orandor_1_no_out_trans
INFO[0000] running tests: [index_merge_sqlgen_exprs_orandor_1_no_out_trans] 
WARN[0000] Create new db&{0 0xc0000b2000 0 {0 0} [0xc0000be000] map[] 0 1 0xc0000b4000 false map[0xc0000be000:map[0xc0000be000:true]] map[] 0 0 0 0 <nil> 0 0 0 0 0x1088dc0} 
./t/index_merge_sqlgen_exprs_orandor_1_no_out_trans.test: ok! 10173 test cases passed, take time 23.954630325 s
INFO[0024] run test [index_merge_sqlgen_exprs_orandor_1_no_out_trans] ok 

$ ./mysql_test -host 127.0.0.1 -port 4000 -user root -params '&allowNativePasswords=true&allowAllFiles=true' index_merge_sqlgen_exprs
INFO[0000] running tests: [index_merge_sqlgen_exprs]    
WARN[0000] Create new db&{0 0xc000010090 0 {0 0} [0xc00013a6c0] map[] 0 1 0xc000102180 false map[0xc00013a6c0:map[0xc00013a6c0:true]] map[] 0 0 0 0 <nil> 0 0 0 0 0x1088dc0} 
./t/index_merge_sqlgen_exprs.test: ok! 533 test cases passed, take time 2.163011253 s
INFO[0002] run test [index_merge_sqlgen_exprs] ok  

Check List

Tests

• Unit test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JmPotato
• rebelice

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/6dea31d6e414aef8017c457f32bab809c2d29f2f

[Yisaer]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 6dea31d

[ti-srebot]

cherry pick to release-6.0 in PR #33304