remove TheiaCon Banner (#653)

fixed #652

src/components/index/Header.js

@@ -106,24 +106,6 @@ const Header = () => (
                     <iframe title="Github Star Count" className="header__github-button" src="https://ghbtns.com/github-btn.html?user=eclipse-theia&repo=theia&type=star&count=true" frameBorder={0} scrolling={0} />
                     <iframe title="Github Fork Count" className="header__github-button" src="https://ghbtns.com/github-btn.html?user=eclipse-theia&repo=theia&type=fork&count=true" frameBorder={0} scrolling={0} />
                 </div>
-                <div className="header__banner">
-                    <a href="https://events.eclipse.org/2024/theiacon/">
-                        <img className="banner__image" src={TheiaConLogo}></img>
-                    </a>
-                    <h1 style={{ fontSize: '2.2rem' }}>
-                        The Call for Presentations is now OPEN for the <a href="https://events.eclipse.org/2024/theiacon/">2024 TheiaCon</a>!<br/>
-                        (Virtual Event | 13 - 14 November, 2024)<br/>
-                        <a href="https://forms.gle/bJvCYnPadUrNwbK6A">Submit your proposal</a> today to be a speaker and <a href="https://www.crowdcast.io/c/theiacon2024">get registered</a>!
-                    </h1>
-                    <div className="header__buttons">
-                        <a className="btn btn--cta" href="https://forms.gle/bJvCYnPadUrNwbK6A" rel="noopener">
-                            Submit Proposal
-                        </a>
-                        <a className="btn btn--cta" href="https://www.crowdcast.io/c/theiacon2024" rel="noopener">
-                            Get registered
-                        </a>
-                    </div>
-                </div>
                 <h1 className="heading-primary">
                     The Eclipse Theia Platform
                 </h1>