gdb/testsuite: remove duplicate test from gdb.cp/maint.exp

gdb/testsuite: remove duplicate test from gdb.cp/maint.exp

I wanted to remove the duplicate test name from gdb.cp/maint.exp.  In
this test we run some checks against different operator names.  For
one operator we test with a variable number of spaces.  However, we
were accidentally testing the one space version twice, and the zero
space version not at all, leading to a duplicate test name.

I could have just changed the duplicate one space version into the
missing zero space version, but I thought it would be neater to wrap
multiple tests in a loop, and check all operators with either zero,
one, or two spaces.

These tests are super quick so take almost no extra time, and this
gives marginally more test coverage.

gdb/testsuite/ChangeLog:

	* gdb.cp/maint.exp (test_first_component): Run more tests with a
	variable number of spaces, this removes the duplicate testing of
	'operator ->' which existed before.