fix: resolve data race in std.Progress.maybeRefresh()

[r00ster91]

It seems we can simply lock the update mutex a little earlier.

Before:

~/Desktop/zig$ zig build -p stage3 -Dsanitize-thread --zig-lib-dir lib
~/Desktop/zig$ stage3/bin/zig run x.zig
AST Lowering [21] zig/number_literal.zig... LLVMSymbolizer: error reading file: No such file or directory
==================
WARNING: ThreadSanitizer: data race (pid=6670)
  Read of size 8 at 0x7ffd5dd43000 by thread T2:
    #0 memcpy <null> (zig+0x1ce7896)

After:

~/Desktop/zig$ zig build -p stage3 -Dsanitize-thread --zig-lib-dir lib
~/Desktop/zig$ stage3/bin/zig run x.zig

Fixes #13072