Update phpcs.xml to use generic PSR-12 rule

Author: joesaunderson

phpcs.xml

@@ -1,40 +1,9 @@
 <?xml version="1.0"?>
-<ruleset name="PHP_CodeSniffer">
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="PHP_CodeSniffer">
   <description>The coding standard for posthog-php project.</description>
 
-  <file>./lib/</file>
-  <file>./test/</file>
+  <file>lib</file>
+  <file>test</file>
 
-  <arg name="tab-width" value="2"/>
-  <rule ref="PSR2">
-    <exclude name="Generic.WhiteSpace.DisallowTabIndent"/>
-    <exclude name="PSR1.Files.SideEffects"/>
-    <exclude name="PSR1.Classes.ClassDeclaration.MissingNamespace"/>
-    <exclude name="PSR1.Classes.ClassDeclaration.MultipleClasses"/>
-    <!-- Enable opening braces can be placed at the same line of class definition -->
-    <exclude name="PSR2.Classes.ClassDeclaration.OpenBraceNewLine"/>
-    <!-- Disable camel caps classname -->
-    <exclude name="Squiz.Classes.ValidClassName.NotCamelCaps"/>
-    <!-- Enable opening braces can be placed at the same line of function definition -->
-    <exclude name="Squiz.Functions.MultiLineFunctionDeclaration.BraceOnSameLine"/>
-  </rule>
-
-  <!-- Set indent size to 2 -->
-  <rule ref="Generic.WhiteSpace.ScopeIndent">
-    <properties>
-      <property name="indent" value="2"/>
-      <property name="tabIndent" value="false"/>
-    </properties>
-  </rule>
-  <!-- Set indent size for multi-line function -->
-  <rule ref="PSR2.Methods.FunctionCallSignature">
-    <properties>
-      <property name="indent" value="2"/>
-    </properties>
-  </rule>
-
-  <rule ref="PSR2.Methods.FunctionCallSignature.ContentAfterOpenBracket">
-    <severity phpcs-only="true">0</severity>
-  </rule>
-
-</ruleset>
+  <rule  ref="PSR12"/>
+</ruleset>