fix: reduce symbolic icon background opacity to 0

Some icons had an opacity of 0.012.

extra/scalable/mimetypes/application-certificate-symbolic.svg

@@ -3,7 +3,7 @@
 <path d="M1.978 2C1.454 2 0.977997 2.476 0.977997 3V13C0.977997 13.524 1.454 14 1.978 14H5.978V12.003H2.978V4.003H13.978V12.003H11.978V14H14.978C15.497 14 15.978 13.565 15.978 13V3C15.978 2.533 15.54 2 14.978 2H1.978Z" fill="#232323"/>
 <path d="M8.7 6.00998C7.94319 6.08094 7.24153 6.43654 6.73682 7.00493C6.23211 7.57331 5.96197 8.31209 5.981 9.07198C5.981 9.86763 6.29707 10.6307 6.85968 11.1933C7.42229 11.7559 8.18535 12.072 8.981 12.072C9.77665 12.072 10.5397 11.7559 11.1023 11.1933C11.6649 10.6307 11.981 9.86763 11.981 9.07198C11.9916 8.64803 11.9123 8.22665 11.7481 7.83562C11.584 7.44458 11.3388 7.09279 11.0288 6.80345C10.7188 6.5141 10.3509 6.29378 9.94948 6.15701C9.54806 6.02024 9.1222 5.97013 8.7 6.00998ZM8.981 7.00998C9.51143 7.00998 10.0201 7.2207 10.3952 7.59577C10.7703 7.97084 10.981 8.47955 10.981 9.00998C10.981 9.54042 10.7703 10.0491 10.3952 10.4242C10.0201 10.7993 9.51143 11.01 8.981 11.01C8.45056 11.01 7.94186 10.7993 7.56678 10.4242C7.19171 10.0491 6.981 9.54042 6.981 9.00998C6.981 8.47955 7.19171 7.97084 7.56678 7.59577C7.94186 7.2207 8.45056 7.00998 8.981 7.00998Z" fill="#232323"/>
 <path fill-rule="evenodd" clip-rule="evenodd" d="M6.98 11V16L8.98 14L10.98 16V11" fill="#232323"/>
-<path d="M-0.0199966 0H15.979V16H-0.0199966V0Z" fill="#808080" fill-opacity="0.012"/>
+<path d="M-0.0199966 0H15.979V16H-0.0199966V0Z" fill="#808080" fill-opacity="0.00"/>
 </g>
 <defs>
 <clipPath id="clip0_975_3663">