Merge branch 'rj/maint-grep-remove-redundant-test'

"git grep" stopped spawning an external "grep" long time ago, but a
duplicated test to check internal and external "grep" was left
behind.

* rj/maint-grep-remove-redundant-test:
  t7810-*.sh: Remove redundant test

diff --cc t/t7810-grep.sh
Simple merge