t/README: fix typo

Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/README

@@ -466,7 +466,7 @@ explicitly providing repositories when accessing submodule objects is
 complete or needs to be abandoned for whatever reason (in which case the
 migrated codepaths still retain their performance benefits).
 
-GIT_TEST_REQUIRE_PREREQ=<list> allows specifying a space speparated list of
+GIT_TEST_REQUIRE_PREREQ=<list> allows specifying a space separated list of
 prereqs that are required to succeed. If a prereq in this list is triggered by
 a test and then fails then the whole test run will abort. This can help to make
 sure the expected tests are executed and not silently skipped when their