You can use the yticks and yticklabels functions to control the locations of the ticks and the labels used for those ticks.
Let's make a copy of that plot (so you can see the difference when I run the code in MATLAB Answers) and update the tick locations.
Let's say I want to put ticks every 50 units but only to label multiples of 100.
ticklocations = 0:50:1050;
ticklabels = string(ticklocations);
ticklabels(mod(ticklocations, 100) ~= 0) = "";