[jenkins] Coverage bot: Remove cross-project-tests

[gulfemsavrun]

Directory coverage is recently enabled in https://reviews.llvm.org/D158703, and the following file shows up at the top level because cross-project-tests is also built in the coverage build: cross-project-tests/debuginfo-tests/llvm-prettyprinters/gdb/llvm-support.cpp This patch removes cross-project-tests from the project list.

[yhgu2000]

I don't know if disabling the cross-project-test affects the coverage metrics. Will it be better if we use the --ignore-filename-regex optior to just hide it in the report? In that case, we need to modify the Python script instead.