update mima settings

[julien-truffaut]

I am only getting one error when I run mima locally. It seems to be related to platform specific string.

[error] macros: Failed binary compatibility check against dev.optics:monocle-macro_2.13:3.0.0! Found 2 potential problems
[error]  * static method stringToURL()monocle.PPrism in class monocle.Monocle does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.Monocle.stringToURL")
[error]  * method stringToURL()monocle.PPrism in object monocle.Monocle does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.Monocle.stringToURL")
[error] core: Failed binary compatibility check against dev.optics:monocle-core_2.13:3.0.0! Found 4 potential problems
[error]  * static method stringToURL()monocle.PPrism in class monocle.std.all does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.std.all.stringToURL")
[error]  * method stringToURL()monocle.PPrism in object monocle.std.all does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.std.all.stringToURL")
[error]  * static method stringToURL()monocle.PPrism in class monocle.std.string does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.std.string.stringToURL")
[error]  * method stringToURL()monocle.PPrism in object monocle.std.string does not have a correspondent in current version
[error]    filter with: ProblemFilters.exclude[DirectMissingMethodProblem]("monocle.std.string.stringToURL")

[cquiroz]

LGTM