[chore] Use `grep -E` instead of `egrep` in the root Makefile (#15977)
[chore] Use `grep -E` instead of `egrep` in the root Makefile (#15977)

Use `grep -E` instead of `egrep`

egrep is considered deprecated according to POSIX and within GNU
grep, so use `grep -E`, which is functionally equivalent.

Co-authored-by: Evan Bradley <7ec9efafb38d7f6df6c8b37431ca5cc59dc38bad@users.noreply.github.com>
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector-contrib