[build] Remove obsolete project.toml

I forgot to remove this in the previous build system update.

project.toml

@@ -1,39 +0,0 @@
-# Bonnibel project configuration
-name = "jsix"
-custom-rules = "configs/custom.ninja"
-default-config = "configs/debug.toml"
-
-[variables]
-warnflags = [
-    "-Wformat=2", "-Winit-self", "-Wfloat-equal", "-Winline", "-Wmissing-format-attribute",
-    "-Wmissing-include-dirs", "-Wswitch", "-Wundef", "-Wdisabled-optimization",
-    "-Wpointer-arith", "-Wno-attributes", "-Wno-sign-compare", "-Wno-multichar",
-    "-Wno-div-by-zero", "-Wno-endif-labels", "-Wno-pragmas", "-Wno-format-extra-args",
-    "-Wno-unused-result", "-Wno-deprecated-declarations", "-Wno-unused-function",
-    "-Wno-address-of-packed-member", "-Wno-invalid-offsetof", "-Werror",
-]
-
-ccflags = [
-    "-I${source_root}/src/include",
-    "-I${source_root}/src/include/x86_64",
-    "-fcolor-diagnostics",
-    "-DVERSION_MAJOR=${version_major}",
-    "-DVERSION_MINOR=${version_minor}",
-    "-DVERSION_PATCH=${version_patch}",
-    "-DVERSION_GITSHA=0x${version_sha}",
-    '-DGIT_VERSION=\"${version_major}.${version_minor}.${version_patch}+${version_sha}\"',
-    '-DGIT_VERSION_WIDE=L\"${version_major}.${version_minor}.${version_patch}+${version_sha}\"',
-    "${warnflags}",
-]
-
-asflags = [
-    "-DVERSION_MAJOR=${version_major}",
-    "-DVERSION_MINOR=${version_minor}",
-    "-DVERSION_PATCH=${version_patch}",
-    "-DVERSION_GITSHA=0x${version_sha}",
-    "-I${source_root}/src/include",
-]
-
-cflags = "-std=c11"
-cxxflags = "-std=c++17"
-