fix(grafana dashboard): datasource.uid should point to ${datasource}

[aceforeverd]

instead specific uid string, for non-existed uid, grafana ui will default points to ${datasource} menu, that's naughty.

[github-actions]

SDK Test Report

  73 files    73 suites   6m 11s ⏱️
174 tests 171 ✔️ 3 💤 0 ❌
215 runs  212 ✔️ 3 💤 0 ❌

Results for commit 15045ef.

[github-actions]

Linux Test Report

       57 files       186 suites   1h 7m 23s ⏱️
  8 468 tests   8 460 ✔️ 8 💤 0 ❌
12 419 runs  12 411 ✔️ 8 💤 0 ❌

Results for commit 15045ef.

[codecov]

Codecov Report

Merging #1754 (15045ef) into main (c541226) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #1754      +/-   ##
============================================
+ Coverage     73.66%   73.67%   +0.01%     
  Complexity      347      347              
============================================
  Files           614      614              
  Lines        120051   120051              
  Branches       1010     1010              
============================================
+ Hits          88437    88450      +13     
+ Misses        31405    31392      -13     
  Partials        209      209              

Impacted Files	Coverage Δ
src/sdk/sql_cluster_router.cc	53.95% <0.00%> (+0.30%)	⬆️
hybridse/include/base/spin_lock.h	100.00% <0.00%> (+33.33%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c541226...15045ef. Read the comment docs.

[tobegit3hub]

LGTM