t/chainlint/*.test: fix invalid test cases due to mixing quote types

The chainlint self-test code snippets are supposed to represent the body
of a test_expect_success() or test_expect_failure(), yet the contents of
a few tests would have caused the shell to report syntax errors had they
been real test bodies due to the mix of single- and double-quotes.
Although chainlint.sed, with its simplistic heuristics, is blind to this
problem, a future more robust chainlint implementation might not have
such a limitation. Therefore, stop mixing quote types haphazardly in
those tests and unify quoting throughout. While at it, drop chunks of
tests which merely repeat what is already tested elsewhere but with
alternative quotes.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/chainlint/while-loop.test

@@ -1,17 +1,17 @@
 (
-# LINT: 'while, 'do', 'done' do not need "&&"
+# LINT: "while", "do", "done" do not need "&&"
 	while true
 	do
-# LINT: missing "&&" on 'echo'
+# LINT: missing "&&" on "echo"
 		echo foo
 # LINT: last statement of while does not need "&&"
 		cat <<-\EOF
 		bar
 		EOF
-# LINT: missing "&&" on 'done'
+# LINT: missing "&&" on "done"
 	done
 
-# LINT: 'do' on same line as 'while'
+# LINT: "do" on same line as "while"
 	while true; do
 		echo foo &&
 		cat bar