flaky test TestAlterModifyColumnOnPartitionedTableFail

[hawkingrei]

Bug Report

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1. Minimal reproduce step (Required)

    result.go:49: 
        	Error Trace:	/home/jenkins/.tidb/tmp/63a9840cd0739f2c243bb46478607469/sandbox/linux-sandbox/6880/execroot/__main__/bazel-out/k8-fastbuild/bin/ddl/ddl_test_/ddl_test.runfiles/__main__/ddl/result.go:49
        	            				/home/jenkins/.tidb/tmp/63a9840cd0739f2c243bb46478607469/sandbox/linux-sandbox/6880/execroot/__main__/bazel-out/k8-fastbuild/bin/ddl/ddl_test_/ddl_test.runfiles/__main__/ddl/db_partition_test.go:4712
        	Error:      	Not equal: 
        	            	expected: ""
        	            	actual  : "[Warning 1265 Data truncated for column 'a', value is '34 💥💥Longer than 11111']\n"
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -1 +1,2 @@
        	            	+[Warning 1265 Data truncated for column 'a', value is '34 💥💥Longer than 11111']
        	            	 
        	Test:       	TestAlterModifyColumnOnPartitionedTableFail
        	Messages:   	sql:show warnings, args:[]

https://do.pingcap.net/jenkins/blue/rest/organizations/jenkins/pipelines/pingcap/pipelines/tidb/pipelines/ghpr_unit_test/runs/9739/nodes/49/steps/54/log/?start=0

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

[mjonss]

Due to #38669 the warning may or may not show up. I will comment out the show warnings in the test to make it stable.