Describe the issue linked to the documentation

Some UserWarning are present in the dev documentation and need to be fixed.
Here is a list:

• gaussian_process/plot_gpr_prior_posterior.html DOC Fix UserWarning in plot_gpr_prior_posterior #29380
• model_selection/plot_cv_indices.html DOC Removing warnings from plot CV examples #29072
• linear_model/plot_sgd_iris.html DOC Removing warnings from plot_sgd_iris example #29121
• linear_model/plot_logistic_multinomial.html DOC Removing warnings from plot_logistic_multinomial examples #29120
• tree/plot_iris_dtc.html DOC Removing warnings from plot_iris_dtc #29109
• svm/plot_svm_margin.html DOC Remove warning from plot svm margin example #29187
• ensemble/plot_adaboost_twoclass.html DOC Remove warning from plot adaboost twoclass example #29188

Contributors willing to address this issue, please fix one example per pull request. It is ok to fix other warnings or errors in a given example.

Thanks for your help!

Suggest a potential alternative/fix

No response