Help: drop hard-coded white from localized panel titles

The 'Available Commands' and 'Control Flow Statements' Panel titles
live in en.ftl as [bold white]...[/]. White on a light terminal
background is invisible (matches the screenshot showing an empty
bordered box). Switched both to [bold] so the title falls through
to the terminal's default foreground, consistent with the help
headers fixed in e37b59b.

Author: mkrueger

CosmosDBShell/lang/en.ftl

@@ -587,9 +587,9 @@ help-statements = Statements
 help-example = Example
 help-syntax = Syntax
 help-available-commands = Available Commands
-help-available-commands-styled = [bold white]Available Commands[/]
+help-available-commands-styled = [bold]Available Commands[/]
 help-control-flow-statements = Control Flow Statements:
-help-control-flow-statements-styled = [bold white]Control Flow Statements[/]
+help-control-flow-statements-styled = [bold]Control Flow Statements[/]
 help-list-of-available-commands = List of available commands
 help-category-connection = Connection
 help-category-connection-styled = Connection