remove unused icons

src/vs/editor/contrib/documentSymbols/media/files_Filter_Filter_16x_vscode.svg

-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" enable-background="new 0 0 16 16"><style type="text/css">.icon-canvas-transparent{opacity:0;fill:#F6F6F6;} .icon-vs-out{fill:#F6F6F6;} .icon-vs-bg{fill:#424242;} .icon-vs-fg{fill:#F0EFF1;}</style><path class="icon-canvas-transparent" d="M16 16h-16v-16h16v16z" id="canvas"/><path class="icon-vs-out" d="M0 0v3.043l5 6v6.957h6v-6.957l5-6v-3.043h-16z" id="outline" style="display: none;"/><path class="icon-vs-fg" d="M7 14h2v-5.681l5-6v-.319h-12v.319l5 6v5.681z" id="iconFg" style="display: none;"/><path class="icon-vs-bg" d="M10 15h-4v-6.319l-5-6v-1.681h14v1.681l-5 6v6.319zm-3-1h2v-5.681l5-6v-.319h-12v.319l5 6v5.681z" id="iconBg"/></svg>
\ No newline at end of file

src/vs/editor/contrib/documentSymbols/media/files_Filter_Filter_16x_vscode_inverse.svg

-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16" enable-background="new 0 0 16 16"><style type="text/css">.icon-canvas-transparent{opacity:0;fill:#2d2d30;} .icon-vs-out{fill:#2d2d30;} .icon-vs-bg{fill:#c5c5c5;} .icon-vs-fg{fill:#2b282e;}</style><path class="icon-canvas-transparent" d="M16 16h-16v-16h16v16z" id="canvas"/><path class="icon-vs-out" d="M0 0v3.043l5 6v6.957h6v-6.957l5-6v-3.043h-16z" id="outline" style="display: none;"/><path class="icon-vs-fg" d="M7 14h2v-5.681l5-6v-.319h-12v.319l5 6v5.681z" id="iconFg" style="display: none;"/><path class="icon-vs-bg" d="M10 15h-4v-6.319l-5-6v-1.681h14v1.681l-5 6v6.319zm-3-1h2v-5.681l5-6v-.319h-12v.319l5 6v5.681z" id="iconBg"/></svg>
\ No newline at end of file