Remove unused methods

[ Merge of http://go/wvgerrit/16405/ ]

Methods in string conversion and license request tests were not being used.
This was detected by static analysis cppcheck reports.

b/26349052

Change-Id: I44779abf6b6fdc01b5391bff7d47be1d20ef84d2

libwvdrmengine/cdm/core/src/string_conversions.cpp

@@ -157,18 +157,6 @@ std::string IntToString(int value) {
   return out_string;
 }
 
-std::string UintToString(unsigned int value) {
-  // log10(2) ~= 0.3 bytes needed per bit or per byte log10(2**8) ~= 2.4.
-  // So round up to allocate 3 output characters per byte.
-  const int kOutputBufSize = 3 * sizeof(unsigned int);
-  char buffer[kOutputBufSize];
-  memset(buffer, 0, kOutputBufSize);
-  snprintf(buffer, kOutputBufSize, "%u", value);
-
-  std::string out_string(buffer);
-  return out_string;
-}
-
 int64_t htonll64(int64_t x) {  // Convert to big endian (network-byte-order)
   union {
     uint32_t array[2];