starship: remove deprecated character.symbol setting

Fixes #1550
PR #1695

modules/programs/starship.nix

@@ -50,7 +50,10 @@ in {
             "$character"
           ];
           scan_timeout = 10;
-          character.symbol = "➜";
+          character = {
+            success_symbol = "➜";
+            error_symbol = "➜";
+          };
         }
       '';
       description = ''

tests/modules/programs/starship/settings-expected.toml

@@ -18,7 +18,8 @@ style = "bold yellow"
 threshold = 30
 
 [character]
-symbol = "➜"
+error_symbol = "➜"
+success_symbol = "➜"
 
 [memory_usage]
 threshold = -1

tests/modules/programs/starship/settings.nix

@@ -17,7 +17,10 @@ with lib;
             "$character"
           ];
           scan_timeout = 10;
-          character.symbol = "➜";
+          character = {
+            success_symbol = "➜";
+            error_symbol = "➜";
+          };
           package.disabled = true;
           memory_usage.threshold = -1;
           aws.style = "bold blue";