fix(Modal): fix button ref (#5699)

This change fixes `.button` internal class property of `<Modal>` not
being updated with the internal primary button, due to stale prop name
used for `<Button>` for its `ref`.

Fixes #5685.

Author: asudoh

packages/react/src/components/Modal/Modal.js

@@ -408,7 +408,7 @@ export default class Modal extends Component {
               kind={danger ? 'danger' : 'primary'}
               disabled={primaryButtonDisabled}
               onClick={onRequestSubmit}
-              inputref={this.button}>
+              ref={this.button}>
               {primaryButtonText}
             </Button>
           </div>

packages/react/src/components/ModalWrapper/__snapshots__/ModalWrapper-test.js.snap

@@ -172,33 +172,6 @@ exports[`ModalWrapper should render 1`] = `
             </ForwardRef(Button)>
             <ForwardRef(Button)
               disabled={false}
-              inputref={
-                Object {
-                  "current": <button
-                    aria-label="close the modal"
-                    class="bx--modal-close"
-                    title="close the modal"
-                    type="button"
-                  >
-                    <svg
-                      aria-label="close the modal"
-                      class="bx--modal-close__icon"
-                      focusable="false"
-                      height="20"
-                      preserveAspectRatio="xMidYMid meet"
-                      role="img"
-                      style="will-change: transform;"
-                      viewBox="0 0 32 32"
-                      width="20"
-                      xmlns="http://www.w3.org/2000/svg"
-                    >
-                      <polygon
-                        points="24 9.4 22.6 8 16 14.6 9.4 8 8 9.4 14.6 16 8 22.6 9.4 24 16 17.4 22.6 24 24 22.6 17.4 16 24 9.4"
-                      />
-                    </svg>
-                  </button>,
-                }
-              }
               kind="primary"
               onClick={[Function]}
               tabIndex={0}
@@ -207,33 +180,6 @@ exports[`ModalWrapper should render 1`] = `
               <button
                 className="bx--btn bx--btn--primary"
                 disabled={false}
-                inputref={
-                  Object {
-                    "current": <button
-                      aria-label="close the modal"
-                      class="bx--modal-close"
-                      title="close the modal"
-                      type="button"
-                    >
-                      <svg
-                        aria-label="close the modal"
-                        class="bx--modal-close__icon"
-                        focusable="false"
-                        height="20"
-                        preserveAspectRatio="xMidYMid meet"
-                        role="img"
-                        style="will-change: transform;"
-                        viewBox="0 0 32 32"
-                        width="20"
-                        xmlns="http://www.w3.org/2000/svg"
-                      >
-                        <polygon
-                          points="24 9.4 22.6 8 16 14.6 9.4 8 8 9.4 14.6 16 8 22.6 9.4 24 16 17.4 22.6 24 24 22.6 17.4 16 24 9.4"
-                        />
-                      </svg>
-                    </button>,
-                  }
-                }
                 onClick={[Function]}
                 tabIndex={0}
                 type="button"