Update error messages per review feedback.

Author: resistor

lld/ELF/Arch/RISCV.cpp

@@ -1505,8 +1505,8 @@ void RISCV::scanSectionImpl(InputSectionBase &sec, Relocs<RelTy> rels) {
     } else if (!rvVendor.empty()) {
       Err(ctx) << getErrorLoc(ctx, loc)
                << "unknown vendor-specific relocation (" << type.v
-               << ") in vendor namespace \"" << rvVendor << "\" against symbol "
-               << &sym;
+               << ") in namespace '" << rvVendor << "' against symbol '" << &sym
+               << "'";
       rvVendor = "";
       continue;
     }

lld/test/riscv-vendor-relocations.s

@@ -15,4 +15,4 @@ TARGET:
   nop
 
 # CHECK: error: {{.*}}:(.text+0x4): malformed consecutive R_RISCV_VENDOR relocations
-# CHECK: error: {{.*}}:(.text+0x4): unknown vendor-specific relocation (255) in vendor namespace "INVALID_VENDOR" against symbol TARGET
+# CHECK: error: {{.*}}:(.text+0x4): unknown vendor-specific relocation (255) in namespace 'INVALID_VENDOR' against symbol 'TARGET'