Fix links to solvers
Fix links to solvers

Some links to solvers (e.g. GLPK) were spelled `(solver/glpk)` instead of `(/solver/glpk)` in Markdown, so that resulting URL was https://yalmip.github.io/allsolvers/solver/glpk (Page Not Found error) instead of https://yalmip.github.io/solver/glpk
yalmip/yalmip.github.io,yalmip/yalmip.github.io,yalmip/yalmip.github.io