Drop bcmath dependency

we haven't used bcmath since the days of 32-bit.

composer.json

@@ -7,7 +7,6 @@
    "require": {
       "php": ">=7.3.0",
       "php-64bit": "*",
-      "ext-bcmath": "*",
       "ext-curl": "*",
       "ext-ctype": "*",
       "ext-date": "*",

composer.lock

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "2c44138f2052c259a201871d4d423947",
+    "content-hash": "898e2d529d8aec83866a2bbaa867e23f",
     "packages": [
         {
             "name": "adhocore/json-comment",
@@ -2749,7 +2749,6 @@
     "platform": {
         "php": ">=7.3.0",
         "php-64bit": "*",
-        "ext-bcmath": "*",
         "ext-curl": "*",
         "ext-ctype": "*",
         "ext-date": "*",

src/pocketmine/PocketMine.php

@@ -73,7 +73,6 @@ namespace pocketmine {
 		}
 
 		$extensions = [
-			"bcmath" => "BC Math",
 			"curl" => "cURL",
 			"ctype" => "ctype",
 			"date" => "Date",