minor symfony#16737 [Yaml] minor CS cleaning (mhujer)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes symfony#16737).

Discussion
----------

[Yaml] minor CS cleaning

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

PHPStorm reported different types of coding style suggestions along the Symfony codebase. I've fixed some of them in the Yaml compontent and I have two questions:
1) What is the correct branch for such changes? Not all of them can be fixed in 2.3/2.8, for example `ParserTest`'s docblock is different there.
2) Should I create similar PRs for other components or is there a plan to do all such fixes at once someday in the future (e.g. after 2.8/3.0 is released)?

Commits
-------

613804d [Yaml] minor CS cleaning

Author: fabpot

src/Symfony/Component/Yaml/Parser.php

@@ -311,7 +311,7 @@ private function getNextEmbedBlock($indentation = null, $inSequence = false)
         if (null === $indentation) {
             $newIndent = $this->getCurrentLineIndentation();
 
-            $unindentedEmbedBlock = $this->isStringUnIndentedCollectionItem($this->currentLine);
+            $unindentedEmbedBlock = $this->isStringUnIndentedCollectionItem();
 
             if (!$this->isCurrentLineEmpty() && 0 === $newIndent && !$unindentedEmbedBlock) {
                 throw new ParseException('Indentation problem.', $this->getRealCurrentLineNb() + 1, $this->currentLine);
@@ -337,7 +337,7 @@ private function getNextEmbedBlock($indentation = null, $inSequence = false)
             return;
         }
 
-        $isItUnindentedCollection = $this->isStringUnIndentedCollectionItem($this->currentLine);
+        $isItUnindentedCollection = $this->isStringUnIndentedCollectionItem();
 
         // Comments must not be removed inside a block scalar
         $removeCommentsPattern = '~'.self::BLOCK_SCALAR_HEADER_PATTERN.'$~';
@@ -350,7 +350,7 @@ private function getNextEmbedBlock($indentation = null, $inSequence = false)
                 $removeComments = !preg_match($removeCommentsPattern, $this->currentLine);
             }
 
-            if ($isItUnindentedCollection && !$this->isStringUnIndentedCollectionItem($this->currentLine) && $newIndent === $indent) {
+            if ($isItUnindentedCollection && !$this->isStringUnIndentedCollectionItem() && $newIndent === $indent) {
                 $this->moveToPreviousLine();
                 break;
             }
@@ -653,7 +653,7 @@ private function isNextLineUnIndentedCollection()
         if (
             $this->getCurrentLineIndentation() == $currentIndentation
             &&
-            $this->isStringUnIndentedCollectionItem($this->currentLine)
+            $this->isStringUnIndentedCollectionItem()
         ) {
             $ret = true;
         }