README: Remove Coverity badge
README: Remove Coverity badge

It's dead Jim.

It was less and less relevant anyway, as new code is all written in
Kotlin nowadays.

Signed-off-by: Alexandre Montplaisir <0b9d8e7da097b5bbfe36e48cca5acfe475f18227@efficios.com>

lttng/lttng-scope,alexmonthy/lttng-scope,alexmonthy/lttng-scope,alexmonthy/lttng-scope,lttng/lttng-scope,lttng/lttng-scope,lttng/lttng-scope