No, it is not a violation of the GPL to remove any files (including the license file) before uploading. The GPL does not place any restriction on use or modification of a work, but rather only on redistribution of the work or distribution of a modified/derivative work.
In fact, the license states this scope explicitly:
Activities other than copying, distribution and modification are not covered by this License; they are outside its scope.
Further, copying is only within the scope of the license when such modifications are distributed [emphasis and emphasis added]:
You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions…
Note that “modify your copy or copies of the Program or any portion of it” is separated from “copy and distribute such modifications”. The notice and license requirements apply only to distributed works.
The GPL doesn’t compel you to do anything whatsoever with a work that you use and modify, but do not distribute.