Fix linter checks

[hanzei]

The CI linter checks are broken. The CI job fails with:

golangci-lint run ./...
Error: server/plugin.go:39:28: unused-parameter: parameter 'c' seems to be unused, consider removing or renaming it as _ (revive)
func (p *Plugin) ServeHTTP(c *plugin.Context, w http.ResponseWriter, r *http.Request) {
                           ^
Error: server/plugin.go:90:82: unused-parameter: parameter 'mmUserID' seems to be unused, consider removing or renaming it as _ (revive)
func (p *Plugin) httpMeetingSaveSettings(w http.ResponseWriter, r *http.Request, mmUserID string) {
                                                                                 ^
Error: server/plugin.go:115:81: unused-parameter: parameter 'mmUserID' seems to be unused, consider removing or renaming it as _ (revive)
func (p *Plugin) httpMeetingGetSettings(w http.ResponseWriter, r *http.Request, mmUserID string) {
                                                                                ^
Error: server/command.go:44:33: unused-parameter: parameter 'c' seems to be unused, consider removing or renaming it as _ (revive)
func (p *Plugin) ExecuteCommand(c *plugin.Context, args *model.CommandArgs) (*model.CommandResponse, *model.AppError) {
                                ^
Error: server/command.go:219:37: unused-parameter: parameter 'args' seems to be unused, consider removing or renaming it as _ (revive)
func (p *Plugin) executeCommandHelp(args *model.CommandArgs) *model.CommandResponse {
                                    ^
make: *** [Makefile:46: check-style] Error 1
Error: Process completed with exit code 2.

See https://github.com/mattermost/mattermost-plugin-agenda/actions/runs/8660923579/job/23749777528?pr=112

[webstradev]

I'll pick this one up.

Only question is what you want to do with the unused function.
the unused params are easily ignored with _

But the getConfiguration function is currently not used. Removing it doesn't break anything but maybe its better to set a lintignore there to keep the functionality?