Sample config: remove references to setting public_baseurl

Since it has a default now, you don't need to set it.

docs/sample_config.yaml

@@ -1249,7 +1249,7 @@ oembed:
 # in on this server.
 #
 # (By default, no suggestion is made, so it is left up to the client.
-# This setting is ignored unless public_baseurl is also set.)
+# This setting is ignored unless public_baseurl is also explicitly set.)
 #
 #default_identity_server: https://matrix.org
 
@@ -1274,8 +1274,6 @@ oembed:
 # by the Matrix Identity Service API specification:
 # https://matrix.org/docs/spec/identity_service/latest
 #
-# If a delegate is specified, the config option public_baseurl must also be filled out.
-#
 account_threepid_delegates:
     #email: https://example.com     # Delegate email sending to example.com
     #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
@@ -1965,11 +1963,10 @@ sso:
     # phishing attacks from evil.site. To avoid this, include a slash after the
     # hostname: "https://my.client/".
     #
-    # If public_baseurl is set, then the login fallback page (used by clients
-    # that don't natively support the required login flows) is whitelisted in
-    # addition to any URLs in this list.
+    # The login fallback page (used by clients that don't natively support the
+    # required login flows) is whitelisted in addition to any URLs in this list.
     #
-    # By default, this list is empty.
+    # By default, this list contains only the login fallback page.
     #
     #client_whitelist:
     #  - https://riot.im/develop

synapse/config/registration.py

@@ -229,7 +229,7 @@ def generate_config_section(self, generate_secrets=False, **kwargs):
         # in on this server.
         #
         # (By default, no suggestion is made, so it is left up to the client.
-        # This setting is ignored unless public_baseurl is also set.)
+        # This setting is ignored unless public_baseurl is also explicitly set.)
         #
         #default_identity_server: https://matrix.org
 
@@ -254,8 +254,6 @@ def generate_config_section(self, generate_secrets=False, **kwargs):
         # by the Matrix Identity Service API specification:
         # https://matrix.org/docs/spec/identity_service/latest
         #
-        # If a delegate is specified, the config option public_baseurl must also be filled out.
-        #
         account_threepid_delegates:
             #email: https://example.com     # Delegate email sending to example.com
             #msisdn: http://localhost:8090  # Delegate SMS sending to this local process

synapse/config/sso.py

@@ -125,11 +125,10 @@ def generate_config_section(self, **kwargs):
             # phishing attacks from evil.site. To avoid this, include a slash after the
             # hostname: "https://my.client/".
             #
-            # If public_baseurl is set, then the login fallback page (used by clients
-            # that don't natively support the required login flows) is whitelisted in
-            # addition to any URLs in this list.
+            # The login fallback page (used by clients that don't natively support the
+            # required login flows) is whitelisted in addition to any URLs in this list.
             #
-            # By default, this list is empty.
+            # By default, this list contains only the login fallback page.
             #
             #client_whitelist:
             #  - https://riot.im/develop