Tags::__toString(): remove redundant type casts

Psalm flags these type casts as redundant:
```
ERROR: RedundantCastGivenDocblockType - src/DocBlock/Tags/Author.php:80:23 - Redundant cast to string given docblock-provided type (see https://psalm.dev/263)
        $authorName = (string) $this->authorName;

ERROR: RedundantCastGivenDocblockType - src/DocBlock/Tags/Example.php:150:21 - Redundant cast to string given docblock-provided type (see https://psalm.dev/263)
        $filePath = (string) $this->filePath;

ERROR: RedundantCastGivenDocblockType - src/DocBlock/Tags/Link.php:74:17 - Redundant cast to string given docblock-provided type (see https://psalm.dev/263)
        $link = (string) $this->link;

ERROR: RedundantCastGivenDocblockType - src/DocBlock/Tags/Method.php:228:23 - Redundant cast to string given docblock-provided type (see https://psalm.dev/263)
        $methodName = (string) $this->methodName;
```

I have verified each and can confirm that these are redundant. They are probably a left-over from the time when the `__construct()` method in these classes did not yet have type declarations.

src/DocBlock/Tags/Author.php

@@ -79,7 +79,7 @@ final class Author extends BaseTag implements Factory\StaticMethod
             $authorEmail = '';
         }
 
-        $authorName = (string) $this->authorName;
+        $authorName = $this->authorName;
 
         return $authorName . ($authorEmail !== '' ? ($authorName !== '' ? ' ' : '') . $authorEmail : '');
     }

src/DocBlock/Tags/Example.php

@@ -148,7 +148,7 @@ final class Example implements Tag, Factory\StaticMethod
      */
     public function __toString(): string
     {
-        $filePath = (string) $this->filePath;
+        $filePath = $this->filePath;
         $isDefaultLine = $this->startingLine === 1 && $this->lineCount === 0;
         $startingLine = !$isDefaultLine ? (string) $this->startingLine : '';
         $lineCount = !$isDefaultLine ? (string) $this->lineCount : '';

src/DocBlock/Tags/Link.php

@@ -71,7 +71,7 @@ final class Link extends BaseTag implements Factory\StaticMethod
             $description = '';
         }
 
-        $link = (string) $this->link;
+        $link = $this->link;
 
         return $link . ($description !== '' ? ($link !== '' ? ' ' : '') . $description : '');
     }

src/DocBlock/Tags/Method.php

@@ -228,7 +228,7 @@ final class Method extends BaseTag implements Factory\StaticMethod
 
         $returnType = (string) $this->returnType;
 
-        $methodName = (string) $this->methodName;
+        $methodName = $this->methodName;
 
         return $static
             . ($returnType !== '' ? ($static !== '' ? ' ' : '') . $returnType : '')