The VHDL language reference manual states that:

Every design unit except package STANDARD is assumed to contain the following implicit context items as part of its context clause:

    library STD, WORK;
    use STD.STANDARD.all;

Hence, any extra library statement in your VHDL code that includes STD or WORK is pointless, as is any use clause that includes std.standard.all. Hardly anybody would type the use clause, but quite some people start all of their files with two extra library clauses.

It is good practice not to include use clauses for libraries STD and WORK. Sigasi Studio flags as warning if they appear.

library IEEE, STD, WORK;

Project specific setting of this rule

This rule can be disabled for your project, or its severity can be modified in the project linting settings.

Manual configuration in ${project location}/.settings/com.sigasi.hdt.vhdl.linting.prefs:

49/severity/<project>=IGNORE