Hi,
Open the manifest.xsf in any editor. And search for ‘xsf:customValidation'. There change the ‘shortMessage' value to a blank value.
<xsf:customValidation>
<xsf:errorCondition match="/my:myFields/my:field1" expressionContext="." expression=". = """>
<xsf:errorMessage type="modal" shortMessage=" ">dsgsdfg</xsf:errorMessage>
</xsf:errorCondition>
</xsf:customValidation>
The value of match attribute in the error condition should be the xpath of the field to which you are providing the validation.
Hope this will help to you.
Note: Make sure you have a back up of manifest.xsf while doing these changes.