Ports/libicu: Remove obsolete <cmath> header patch

All issues with `cmath` have been resolved quite some time ago, and
ICU seems to build without issues.

Ports/libicu/patches/std.patch

@@ -1,48 +0,0 @@
-diff -Naur source/i18n/decimfmt.cpp source.serenity/i18n/decimfmt.cpp
---- source/i18n/decimfmt.cpp	2021-05-11 18:48:28.172956656 +0200
-+++ source.serenity/i18n/decimfmt.cpp	2021-05-11 18:47:42.222070235 +0200
-@@ -9,7 +9,7 @@
- // Helpful in toString methods and elsewhere.
- #define UNISTR_FROM_STRING_EXPLICIT
- 
--#include <cmath>
-+#include <math.h>
- #include <cstdlib>
- #include <stdlib.h>
- #include "unicode/errorcode.h"
-diff -Naur source/i18n/number_decimalquantity.cpp source.serenity/i18n/number_decimalquantity.cpp
---- source/i18n/number_decimalquantity.cpp	2021-05-11 18:48:28.172956656 +0200
-+++ source.serenity/i18n/number_decimalquantity.cpp	2021-05-11 18:48:02.715798916 +0200
-@@ -6,7 +6,7 @@
- #if !UCONFIG_NO_FORMATTING
- 
- #include <cstdlib>
--#include <cmath>
-+#include <math.h>
- #include <limits>
- #include <stdlib.h>
- 
-diff -Naur source/i18n/number_utils.cpp source.serenity/i18n/number_utils.cpp
---- source/i18n/number_utils.cpp	2021-05-11 18:48:28.172956656 +0200
-+++ source.serenity/i18n/number_utils.cpp	2021-05-11 18:47:22.298352531 +0200
-@@ -10,7 +10,7 @@
- #define UNISTR_FROM_STRING_EXPLICIT
- 
- #include <stdlib.h>
--#include <cmath>
-+#include <math.h>
- #include "number_decnum.h"
- #include "number_types.h"
- #include "number_utils.h"
-diff -Naur source/i18n/reldatefmt.cpp source.serenity/i18n/reldatefmt.cpp
---- source/i18n/reldatefmt.cpp	2021-05-11 18:48:28.172956656 +0200
-+++ source.serenity/i18n/reldatefmt.cpp	2021-05-11 18:46:45.380973593 +0200
-@@ -14,7 +14,7 @@
- 
- #if !UCONFIG_NO_FORMATTING && !UCONFIG_NO_BREAK_ITERATION
- 
--#include <cmath>
-+#include <math.h>
- #include <functional>
- #include "unicode/dtfmtsym.h"
- #include "unicode/ucasemap.h"