fix(meta): remove runtime.HttpBodyMarshaler from gateway stack

[GeorgeMac]

Fixes FLI-176

This fixes the case where the /meta prefixed endpoints would return 500 (and panic server-side) when authentication was required and no authentication was provided.
Additionally, this only occurred when the Accept header was explicitly set to application/json.

The accept header caused the HttpBodyMarshaler to be invoked. When authentication was not provided, the resulting body was an error and not the expected HttpBody instance. This marshaller was fallback to an embedded marshaller in this instance. This wasn't being set and was therefore nil, causing a panic at runtime.

Update: After reflecting on the behaviour that this only failed when the Accept header was presented, I looked into whether you need to explicitly set the HttpBodyMarshaler and it turns out you don't.
The Marshal stack handles the presence of HttpBody without it.

In 8d2f433 I drop them altogether and it behaves as it should.

[codecov-commenter]

Codecov Report

Merging #1277 (9385f51) into main (5af0757) will decrease coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1277      +/-   ##
==========================================
- Coverage   79.82%   79.63%   -0.19%     
==========================================
  Files          42       42              
  Lines        3217     3217              
==========================================
- Hits         2568     2562       -6     
- Misses        521      525       +4     
- Partials      128      130       +2     

Impacted Files	Coverage Δ
internal/storage/oplock/sql/sql.go	90.82% <0.00%> (-5.51%)	⬇️

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[GeorgeMac]

The last commit from this message has the failing reproduction test case:

GET http://0.0.0.0:8080/meta/info
 ✘ status 401 (actual: 500)

GET http://0.0.0.0:8080/meta/config
 ✘ status 401 (actual: 500)