t1300: fix config file syntax error descriptions

Three tests in t1300-config.sh check that "git config --get" barfs when
the config file contains various syntax errors: key=value pair without
equals sign, broken section line, and broken value string.  The sample
config files include a comment describing the kind of broken syntax.
This description seems to have been copy-pasted from the "broken section
line" sample to the other two samples.

Fix descriptions of broken config file syntax in samples used in
t1300-config.sh.

Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1300-config.sh

@@ -1571,7 +1571,7 @@ test_expect_success 'git config --edit respects core.editor' '
 # malformed configuration files
 test_expect_success 'barf on syntax error' '
 	cat >.git/config <<-\EOF &&
-	# broken section line
+	# broken key=value
 	[section]
 	key garbage
 	EOF
@@ -1591,7 +1591,7 @@ test_expect_success 'barf on incomplete section header' '
 
 test_expect_success 'barf on incomplete string' '
 	cat >.git/config <<-\EOF &&
-	# broken section line
+	# broken value string
 	[section]
 	key = "value string
 	EOF