docs: multiple small fixes around databases (#14321)

* docs: multiple small fixes around databases

* add link to postgres SSL options

docs/src/pages/docs/Connecting to Databases/mysql.mdx

@@ -8,21 +8,16 @@ version: 1
 
 ## MySQL
 
-The recommended connector library for MySQL is [mysqlclient](https://pypi.org/project/mysqlclient/).
+The recommended connector library for MySQL is [mysql-connector-python](https://pypi.org/project/mysql-connector-python/).
 
-Set up the Connection String using the following settings:
+Here's the connection string:
 
-User Name: UserName
+```
-Password: DBPassword
+mysql+mysqlconnector://{username}:{password}@{host}/{database}
-Database Host:
+```
-- For Localhost or docker running Linux: localhost or 127.0.0.1
+
+Host:
+- For Localhost or Docker running Linux: `localhost` or `127.0.0.1`
 - For On Prem: IP address or Host name
-- For AWS Endpoint
+- For Docker running in OSX: `docker.for.mac.host.internal`
-- For Docker running in OSX: docker.for.mac.host.internal
+Port: `3306` by default
-Database Name: Database Name
-Port: default 3306
-
-Connection String
-```
-mysql://<UserName>:<DBPassword>@<Database Host>/<Database Name>
-```

docs/src/pages/docs/Connecting to Databases/postgres.mdx

@@ -25,15 +25,18 @@ Postgres sample connection parameters:
 The connection string looks like:
 
 ```
-postgresql+psycopg2://{username}:{password}@{host}:{port}/{database}
+postgresql://{username}:{password}@{host}:{port}/{database}
 ```
 
-Extra parameters:
+You can require SSL by adding `?sslmode=require` at the end:
 
 ```
-?sslmode=require
+postgresql://{username}:{password}@{host}:{port}/{database}?sslmode=require
 ```
 
+You can read about the other SSL modes that Postgres supports in
+[Table 31-1 from this documentation](https://www.postgresql.org/docs/9.1/libpq-ssl.html).
+
 More information about PostgreSQL connection options can be found in the
 [SQLAlchemy docs](https://docs.sqlalchemy.org/en/13/dialects/postgresql.html#module-sqlalchemy.dialects.postgresql.psycopg2)
 and the

docs/src/pages/docs/Connecting to Databases/presto.mdx

@@ -14,13 +14,24 @@ The expected connection string is formatted as follows:
 
 ```
 presto://{hostname}:{port}/{database}
-e.g.
+```
-presto://presto.example.com:8080/hive
+
+You can pass in a username and password as well:
+
+```
+presto://{username}:{password}@{hostname}:{port}/{database}
+```
+
+Here is an example connection string with values:
+
+```
+presto://datascientist:securepassword@presto.example.com:8080/hive
 ```
 
 By default Superset assumes the most recent version of Presto is being used when querying the
 datasource. If you’re using an older version of Presto, you can configure it in the extra parameter:
 
+
 ```
 {
     "version": "0.123"