Fix whitespace issues in testcases

This adds a newline at the end of the file, which is helpful for git
diff display.

Author: matthijskooijman

test/src/String/test_comparisonFunc.cpp

@@ -104,4 +104,4 @@ TEST_CASE ("Testing String::endsWith(const String &)", "[String-endsWith-10]")
     arduino::String str2("Helo");
     REQUIRE(str1.endsWith(str2) == 0);
   }
-}
+}

test/src/String/test_concat.cpp

@@ -99,4 +99,4 @@ TEST_CASE ("Testing String::concat(const __FlashStringHelper *)", "[String-conca
   arduino::String str1("Hello");
   REQUIRE(str1.concat(F(" Arduino")) == 1);
   REQUIRE(strcmp(str1.c_str(), "Hello Arduino") == 0);
-}
+}

test/src/String/test_operators.cpp

@@ -153,4 +153,4 @@ TEST_CASE ("Testing & String::operator = (StringSumHelper &&)", "[String-operato
   arduino::String str1("Arduino");
   str1 = static_cast<arduino::StringSumHelper&&>(str+ch);
   REQUIRE(str1.compareTo("Hello!") == 0);
-}
+}

test/src/String/test_substring.cpp

@@ -35,4 +35,4 @@ TEST_CASE ("Testing String::substring(unsigned int, unsigned int)", "[String-sub
     arduino::String str2("ello");
     REQUIRE(str2.compareTo(str1.substring(9,1)) == 0);
   }
-}
+}