[rmodels] Fix minimum rings validation in DrawCapsule and DrawCapsuleWires

[LuisR385]

Description

This PR fixes a missing validation for the rings parameter in DrawCapsule() and DrawCapsuleWires().
Currently, slices has a minimum guard (if (slices < 3) slices = 3;), but rings does not, which can cause rendering artifacts or crashes if a user passes 0 or negative values.

Changes

• Added if (rings < 1) rings = 1; to DrawCapsule() in rmodels.c.
• Added if (rings < 1) rings = 1; to DrawCapsuleWires() in rmodels.c.

Visuals

How to test / Reproduce

Passing 0 to slices or rings previously caused an issue.

// Example to reproduce the issue (passing 0 to slices/rings)
DrawCapsule((Vector3){0.0f, 0.5f, 7.0f}, (Vector3){0.0f, 1.5f, 7.0f}, 0.3f, 8, 0, LIME);
DrawCapsuleWires((Vector3){7.0f, 0.5f, 7.0f}, (Vector3){7.0f, 1.5f, 7.0f}, 0.3f, 8, 0, MAGENTA);

[raysan5]

@LuisR385 I'm merging this PR but note that raylib does not validate all the input data received by users, it's expected that users provide valid data. Validating all required data will imply adding lot of code for maintainability, also, validation changes input data so results could be confusing for some users.

[LuisR385]

Thanks for merging this and for the clarification regarding the validation policy. It makes sense!