Generic/RequireExplicitBooleanOperatorPrecedence: remove

unreachable condition

This commit reverts the changes to the
`Generic.CodeAnalysis.RequireExplicitBooleanOperatorPrecedence` sniff
introduced in
PHPCSStandards/PHPCSExtra@7b38efb.
The sniff's tests remain relevant, so they were preserved.

The original commit was added to fix false positives that the sniff was
triggering when handling boolean operators inside a match (see
PHPCSStandards/PHPCSExtra#271 (review)
-1634348864 and
PHPCSStandards/PHPCSExtra#271 (comment)
). Example:

```php
match (true) {
    $a || ($b && $c) => true,
};
```

I believe the false positive was actually caused by a bug in
`File::findStartOfStatement()`. This bug was then fixed in
b82438f
which rendered the changes to the sniff itself unnecessary and the
removed condition unreachable.

Before this fix, when processing the code example above,
`File::findStartOfStatement()` returned the variable `$a` as the
start of the statement for the `&&` boolean operator. This meant that
`$previous` would be set to `||` and the removed condition would be
needed to ensure the sniff would bail instead of triggering an error.

After this fix, `File::findStartOfStatement()` returns `$b` as the start
of the statement and then `$previous` is set to `false` and the sniff
bails before reaching the removed condition.

Including `Tokens::$blockOpeners` in
`RequireExplicitBooleanOperatorPrecedenceSniff::$searchTargets` was
necessary only for the removed condition, so it was removed as well.

src/Standards/Generic/Sniffs/CodeAnalysis/RequireExplicitBooleanOperatorPrecedenceSniff.php

@@ -53,8 +53,7 @@ class RequireExplicitBooleanOperatorPrecedenceSniff implements Sniff
  */
  public function register()
  {
- $this->searchTargets = Tokens::$booleanOperators;
- $this->searchTargets += Tokens::$blockOpeners;
+ $this->searchTargets = Tokens::$booleanOperators;
  $this->searchTargets[T_INLINE_THEN] = T_INLINE_THEN;
  $this->searchTargets[T_INLINE_ELSE] = T_INLINE_ELSE;
 
@@ -102,12 +101,6 @@ public function process(File $phpcsFile, $stackPtr)
  return;
  }
 
- if (isset(Tokens::$blockOpeners[$tokens[$previous]['code']]) === true) {
- // Beginning of the expression found for a block opener. Needed to
- // correctly handle match arms.
- return;
- }
-
  // We found a mismatching operator, thus we must report the error.
  $error = 'Mixing different binary boolean operators within an expression';
  $error .= ' without using parentheses to clarify precedence is not allowed.';