[libc] fix error: implicit conversion loses floating-point precision: 'double' to 'float' in shared_math_test.cpp (#159934)

This test fails under `-Werror=implicit-float-conversion` (like in our
pre-merge CI) because `dsqrtl` returns a double
https://github.com/llvm/llvm-project/blob/2b937daa1310f7c17a03a0a4a7abf83149e1dc71/libc/src/__support/math/dsqrtl.h#L18

Fixes #159932

Author: makslevental

libc/test/shared/shared_math_test.cpp

@@ -57,7 +57,6 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::cosf(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::coshf(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::cospif(0.0f));
-  EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::dsqrtl(0.0f));
   EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::erff(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp10f(0.0f));
   EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::expf(0.0f));
@@ -77,6 +76,7 @@ TEST(LlvmLibcSharedMathTest, AllDouble) {
   EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::atan2(0.0, 0.0));
   EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::cbrt(0.0));
   EXPECT_FP_EQ(0x1p+0, LIBC_NAMESPACE::shared::cos(0.0));
+  EXPECT_FP_EQ(0x0p+0, LIBC_NAMESPACE::shared::dsqrtl(0.0));
   EXPECT_FP_EQ(0x1p+0, LIBC_NAMESPACE::shared::exp(0.0));
   EXPECT_FP_EQ(0x1p+0, LIBC_NAMESPACE::shared::exp10(0.0));
 }