Fix: Revert Serbian localization to fix build error (#11117)

Author: yaira2

src/Files.App (Package)/Package.appxmanifest

@@ -57,7 +57,6 @@
         <Resource Language="ro-RO"/>
         <Resource Language="ru-RU"/>
         <Resource Language="sk-SK"/>             
-        <Resource Language="sr-SP"/>
         <Resource Language="sv-SE"/>
         <Resource Language="ta"/>
         <Resource Language="th-TH"/>

src/Files.App/Files.App.csproj

@@ -5,7 +5,7 @@
         <AssemblyName>Files</AssemblyName>
         <DefaultLanguage>en-US</DefaultLanguage>
         <AppxBundleAutoResourcePackageQualifiers>Scale|DXFeatureLevel</AppxBundleAutoResourcePackageQualifiers>
-        <AppxDefaultResourceQualifiers>Language=en-US;af;ar;bg;ca;cs-CZ;da;da-DK;de-DE;el;en-GB;es-ES;es-419;fi-FI;fil-PH;fr-FR;he-IL;hi-IN;hu-HU;id-ID;it-IT;ja-JP;ka;ko-KR;lv-LV;nb-NO;nl-NL;or-IN;pl-PL;pt-BR;pt-PT;ro-RO;ru-RU;sk-SK;sr-SP;sv-SE;ta;th-TH;tr-TR;uk-UA;vi;zh-Hans;zh-Hant</AppxDefaultResourceQualifiers>
+        <AppxDefaultResourceQualifiers>Language=en-US;af;ar;bg;ca;cs-CZ;da;da-DK;de-DE;el;en-GB;es-ES;es-419;fi-FI;fil-PH;fr-FR;he-IL;hi-IN;hu-HU;id-ID;it-IT;ja-JP;ka;ko-KR;lv-LV;nb-NO;nl-NL;or-IN;pl-PL;pt-BR;pt-PT;ro-RO;ru-RU;sk-SK;sv-SE;ta;th-TH;tr-TR;uk-UA;vi;zh-Hans;zh-Hant</AppxDefaultResourceQualifiers>
         <TargetPlatformMinVersion>10.0.19041.0</TargetPlatformMinVersion>
         <GenerateAppInstallerFile>False</GenerateAppInstallerFile>
         <AppxPackageSigningTimestampDigestAlgorithm>SHA256</AppxPackageSigningTimestampDigestAlgorithm>