Nuget insists that you want to update to jQuery 2.x
Doh.
The package should not have been updated from 1.x to 2.x. There should have been a separate package for jQuery 2, so .net websites continue to update on the 1.x branch.
There is a workaround.
You must manually change the packages.config in the project. Add a range of allowed versions:
<package id="jQuery" version="1.10.1" targetFramework="net45" allowedVersions="[1.7.1,2)" />
Square bracket "[" is "greater or equal to". So versions greater than 1.7.1 here...
Closing round bracket ")" is less than (not inclusive). So versions up to but not including 2.