scripted-diff: replace remaining Python test equality asserts

Some Python functional tests still use plain `assert x == y`.
The earlier commits convert the ambiguous assert patterns by hand, so this commit can rewrite the remaining safe cases mechanically.
The verify script excludes `wallet_bumpfee.py`, `test_framework/netutil.py`, and `test_framework/authproxy.py`, which still contain assert forms that the plain line-based substitution would misidentify.

-BEGIN VERIFY SCRIPT-
perl -pi -e 's/^(\s*)assert (.+?) == ([^,#]+?)$/\1assert_equal(\2, \3)/' $(git ls-files -- 'test/functional' \
':(exclude)test/functional/wallet_bumpfee.py' ':(exclude)test/functional/test_framework/netutil.py' ':(exclude)test/functional/test_framework/authproxy.py')
-END VERIFY SCRIPT-

test/functional/rpc_help.py

@@ -13,8 +13,8 @@ import re
 
 
 def parse_string(s):
-    assert s[0] == '"'
-    assert s[-1] == '"'
+    assert_equal(s[0], '"')
+    assert_equal(s[-1], '"')
     return s[1:-1]
 
 def process_mapping(fname):