fix: update escape character for sqlite

[sgress454]

fixes fleetdm/fleet#31222

This PR updates the escape character sequences in SQLite to only be ''. From the SQLite docs (see section 3 "Literal Values (Constants)"; emphasis mine):

A string constant is formed by enclosing the string in single quotes ('). A single quote within the string can be encoded by putting two single quotes in a row - as in Pascal. C-style escapes using the backslash character are not supported because they are not standard SQL.

This fix allows the following common query pattern to work:

SELECT * FROM "table_name" WHERE "column_name" LIKE '\_%' ESCAPE '\'

This sets the escape character to a backslash so that single-character wildcared _ char can be escaped, and you can look for values starting with an underscore.