lazygit: fix incorrect bash integration #8669

bashIntegration for lazygit is missing "function" keyword,
which leads to broken `~/.bashrc` file with errors like:

```
bash: ~/.bashrc: line 82: syntax error near unexpected token `('
bash: ~/.bashrc: line 82: `lg() {'
```

modules/programs/lazygit.nix

@@ -88,7 +88,7 @@ in
             "~/.lazygit/newdir";
 
         bashIntegration = ''
-          ${cfg.shellWrapperName}() {
+          function ${cfg.shellWrapperName}() {
               export LAZYGIT_NEW_DIR_FILE=${lazygitNewDirFilePath}
               command lazygit "$@"
               if [ -f $LAZYGIT_NEW_DIR_FILE ]; then