Remove outdated line from documentation

[trask]

Description:

Documentation for processors states:

Only match_type=strict is allowed if "attributes" are specified.

but this restriction was removed in https://github.com/open-telemetry/opentelemetry-collector/pull/928/files#diff-4548db28578c2ac90e2b277f24654cfa24fd0f99d854e0fcc4b50871c0b529caL166-R198, and so this doc appears to be outdated.

Testing:

I did not test this, but others (including @tigrannajaryan) have: #1935 (comment)

[btw, in case you're curious my interest in this, we are implementing a subset of this behavior at the java agent layer, as we aren't using otel collector. So far only in our vendor distro, though happy to move it to otel javaagent if/when others are interested.]

[codecov]

Codecov Report

Merging #2233 (f5677db) into master (f4f68db) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2233      +/-   ##
==========================================
- Coverage   92.12%   92.11%   -0.01%     
==========================================
  Files         272      272              
  Lines       15289    15284       -5     
==========================================
- Hits        14085    14079       -6     
  Misses        828      828              
- Partials      376      377       +1     

Impacted Files	Coverage Δ
internal/data/traceid.go	84.61% <0.00%> (-7.70%)	⬇️
internal/data/bytesid.go	80.95% <0.00%> (+4.02%)	⬆️

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[tigrannajaryan]

Thanks @trask