Revert "Merge pull request #3 from WyriHaximus-labs/DEVizzent-openapi-31-8.2-deprecations"

This reverts commit aeedbc7, reversing
changes made to c5a294e.

Author: DEVizzent

src/json/JsonReference.php

@@ -127,7 +127,7 @@ public function getReference(): string
      * which is a value of any type other than a resource.
      */
     #[\ReturnTypeWillChange]
-    public function jsonSerialize(): mixed
+    public function jsonSerialize() //: mixed
     {
         return (object)['$ref' => $this->getReference()];
     }

src/spec/OpenApi.php

@@ -107,7 +107,7 @@ public function performValidation()
      */
     public function getMajorVersion()
     {
-        if (is_string($this->openapi) && preg_match(static::PATTERN_VERSION, $this->openapi, $matches)) {
+        if (preg_match(static::PATTERN_VERSION, $this->openapi, $matches)) {
             switch ($matches[1]) {
                 case '3.0':
                     return static::VERSION_3_0;

src/spec/Paths.php

@@ -195,7 +195,7 @@ public function offsetExists($offset): bool
      * @return PathItem Can return all value types.
      */
     #[\ReturnTypeWillChange]
-    public function offsetGet($offset): mixed
+    public function offsetGet($offset) //: mixed
     {
         return $this->getPath($offset);
     }

src/spec/Responses.php

@@ -185,7 +185,7 @@ public function offsetExists($offset): bool
      * @return mixed Can return all value types.
      */
     #[\ReturnTypeWillChange]
-    public function offsetGet($offset): mixed
+    public function offsetGet($offset) //: mixed
     {
         return $this->getResponse($offset);
     }