Pass -nowarn flag to slience compiler warning during benchmarking

[Friendseeker]

Issue

When running benchmarking, there's lots of compiler warnings from the projects being benchmarked on that do not provide any meaningful info.

Example:

[info] [warn] /tmp/sbt_c424be7/milessabin/shapeless/benchmark-target/62611554399e0d04466da95591253706b2d3020d/core/shared/src/main/managed/shapeless/polynbuilders.scala:445:8: reference to at is ambiguous;
[info] [warn] it is both defined in the enclosing trait Poly11Builder and inherited in the enclosing object build as method at (defined in trait Poly11)
[info] [warn] In Scala 2, symbols inherited from a superclass shadow symbols defined in an outer scope.
[info] [warn] Such references are ambiguous in Scala 3. To continue using the inherited symbol, write `this.at`.
[info] [warn] Or use `-Wconf:msg=legacy-binding:s` to silence this warning. [quickfixable]
[info] [warn]        at(tL(functions))
[info] [warn]        ^
[info] [warn] /tmp/sbt_c424be7/milessabin/shapeless/benchmark-target/62611554399e0d04466da95591253706b2d3020d/core/shared/src/main/managed/shapeless/polynbuilders.scala:485:8: reference to at is ambiguous;
[info] [warn] it is both defined in the enclosing trait Poly12Builder and inherited in the enclosing object build as method at (defined in trait Poly12)
[info] [warn] In Scala 2, symbols inherited from a superclass shadow symbols defined in an outer scope.
[info] [warn] Such references are ambiguous in Scala 3. To continue using the inherited symbol, write `this.at`.
[info] [warn] Or use `-Wconf:msg=legacy-binding:s` to silence this warning. [quickfixable]
[info] [warn]        at(tL(functions))
[info] [warn]        ^
[info] [warn] /tmp/sbt_c424be7/milessabin/shapeless/benchmark-target/62611554399e0d04466da95591253706b2d3020d/core/shared/src/main/managed/shapeless/polynbuilders.scala:525:8: reference to at is ambiguous;

Change

Silence these warnings

Validating the PR

The CI result now omits these warnings.

[eed3si9n]

Thanks!