[Security] Remove unexpected property user-drag

[adaagava]

https://defectdojo.tachi.soramitsu.co.jp/finding/1553231
The W3C specifications define the valid CSS properties. Only the official and browser-specific properties should be used to get the expected impact in the final rendering.

Please remove user-drag property from here:

adar/src/views/About.vue

Line 265 in 861cb5f

user-drag: none;